@ElevenMy main concern with the power is that it's difficult to judge what's "equal"--so she narrowly avoids death today, and then tomorrow...gets stabbed to make up for it? Trips and falls down the stairs shattering every bone in her body? Aside from that, though, this is a narrative-driven RP, there really won't be too many mechanics happening on the player's side so you'd also have to choose to activate the ability which sort of negates the randomness/luck portion of it. I understand it was based off the arcana (which is a nice touch, I like the attention to detail), but I think the cons also outweigh the pros.
For the second point, I'll be blunt; I genuinely don't think a mute character would thrive in this environment. It would be something to overcome and adapt to, yes, but I also think it's too big an obstacle to interaction. While I agree a Crest giving telepathy would potentially solve the issue, that scale of power isn't what I had in mind for the rp. The character and background are solid, future conflicts have basically written themselves, and I think this type of character would go well with the group so far. And ofc I'm definitely willing to hear out any other power you come up with!