Ok, so,
@baraquiel, got to reading your sheet and here's the short story - I think she's firmly a Mary Sue and is rejected right off the bat and should be scrapped.
Here is the longer version.
Lets get into the first portion, via the fact that she slept in a star. I know the rp does take a couple of leaps from reality, but the fact that she slept in a star probably already puts her ahead of the rest of the cast in durability. She would have to have high resistance to heat, kinetic force, radiation, gravity, and so on and so forth. Doesn't that kind of... do much for a demi-god? She sounds more like a god or something.
Moving on to the backstory; I usually don't have any problems with this part of the sheet, but honestly, it just doesn't resonate properly. I understand the backstory revolves around a pc usually, but it has reached a point of ridiculousness with hers. Ok, so Krios is her father and he doesn't want her to know she's a half-blood for some reason, ok. She lived a sheltered life with Virgo and for some reason the constellations all decided to take care of her. I mean, I could probably be alright with her being a half-blood, I'm not adverse to the idea... but this is where she begins to sound like a special snowflake.
Moving on, this is the part where it establishes multiple things - where she sounds more powerful than the cast (and possibly some bosses we haven't introduced yet) and attracts the attention of gods such as Zeus and monsters because of how powerful she was. How powerful does one have to be to catch the eye of Zeus and other monsters? I mean, I've read some myths, but that's besides the point. All attention shifts from whats going on to her exclusively it seems.
Then she tries to kill herself for the sole reason that her life was a lie. She gets put in a star which is probably more like a meteoroid, but that's besides the point. Sleeps for a while and the sphere of light stops her aging.
And despite wanting to kill herself originally, she doesn't try this again at all, even after retaining all her memories after sort of having a backstory similar to Superman in a sense, but eh, that's besides the point. The backstory isn't that good considering she becomes a sort of black hole that draw everything towards her and that also makes her powerful to a problematic degree.
Moving on to the fighting style... there is little in the way of explaining how she actually fights, or rather it shows one thing then shows another. Her fighting style employs certain moves that are inspired by taekwondo and fighting styles from fighting games, as well as dancing. You've compared her to Lili from Tekken.
Oh, and she prefers to fight at long range though. I would expect to see a sort of mix, probably more moves based on the former than the latter portion of this all, but I do not see any special moves that are based on the former portion of this all, rather the latter. Moving on to her moveset, let me breakdown each one and why they don't work.
Spotlight flashes the entire surroundings in a bright light and can blind anyone who can see it. She can still move freely while this is going on. So basically, unless you can ki sense, you're not going to be able to fight her with your eyes. Diantha automatically gimps anyone who can't ki sense since there's no limit to this ability/how long it lasts since it seems she can have it on indefinitely with no repercussions at all. Until the fight ends, a character is permanently blind.
However, even if they got through that, there's still the rest of her kit they have to handle. Star-Forge allows her to create any construct and shape it in any way possible. There is no limit to how many she can create, how quickly she can create them, and how durable they are (while we do know they are less durable than Constellations, we don't know how durable
they are either). So she can trap a character the whole fight and beat them up easily with no set backs or anything unless they have abnormal strength. Again,
what would account for abnormal strength? Is the average nomad able to smash through them?
Meteor Shower just sounds really unfun and unfair on so many levels. This attack pierces through anything except those who have high defense... so you can't block them and have to get out of the way. Again, there seem to be no drawbacks to this move at all, save for people having high defense. I'm pretty sure if this is the case, then no one will probably be able to resist this attack.
Star Wink... like King Crimson, what does it do? Other than being teleported around the battle field, does it have the same properties as a star? If so, then that's a big no already. Other than that, I have no idea what this move does.
Stellar Bursts. Sooooo she created some guns from the same material her constructs were made from and the bullets are stronger than normal bullets and explode on impact... she can also shoot out constructs with them. I already do not like this, based on what I know about the constructs and the fact that, again it seems powerful to the point where there is nothing debilitating about it. What's the point of shooting a bullet that's stronger than a gun when she could possibly shoot out a skyscraper?
Heavenly Light is just no. This means she will always be able to heal outside of caves, buildings and everything else since the sun is a star... and the reason the moon is bright is because of the sun. It isn't clear how fast this allows her to recover her wounds, but based on it all, I'm probably thinking that this heals her fast. Under that assumption, she can use this to heal fast and constantly have an edge on her opponent since there are no real drawbacks to utilizing it at all.
Summon Constellation suffers from problems similar to constructions, save that they are more limited.
Supernova... does 18 times the damage of a single c4, considering it weighs 1 kg. Basically, this will either one shot or kill an opponent outright is what I'm assuming. This sounds like something that would one shot a person. I'm comparing another characters super, Otsana to this one in which she uses 1 kg of C4. This attack roughly matches 18 kg of C4 based on what they've helped explain to me, so once more, this would probably one shot people which I'm not ok with. I know supers are supposed to be flashy, powerful attacks, but I feel this goes... overboard.
And finally Surge Gravitas will basically slowly kill and or instantly kill someone if it makes contact with a person, right? That's what I'm getting, despite it having indirect functions as well. Part of me is already going no since this sounds like a bs way to kill off someone else. While it does have other functions, it either kills a person or is used as a utility. I'm also basing this on how powerful she is too, sooooo yeah...
Moving on to her weaknesses... they aren't that good. She isn't good at close combat, yet the fighting style she was supposedly taught is probably involved in close combat. Heavenly Lights drawbacks are just poor; it can do everything else except cure sicknesses or mental stuff, but has no limits to how fast it can heal, how many times it can be utilized, and so on and so forth. Again, what qualifies as abnormally strong? I feel the one constellation at a time doesn't matter since, you know, it's a super move and I don't think she's going to have the ability to pull it off more than once. Based on this, you're telling me she could probably pull this off consecutively. And finally, I don't think the last two really matter that much since she slept inside a star and is very overpowered with her kit to the point where she is a jack of all trades and master of them all.
My apologies, but I don't really see any way to work this character out other than scrapping it entirely. I'm not adverse to demigods in this rp, at least not right now anyways, but it sounds more like you created a god in a mortal guise rather than a demigod.