The more the merrier! I am ok with her joining. However, I think there are a few provisions which need to be taken into consideration:
1. I really hope to avoid another rough patch like we had starting out. I don't know what your friend's experience is like with D&D, but if she hasn't played before, I think it would be a good thing for her to read through those basic rules I linked to a while back as a bare minimum
2. I also don't know what her experience is like with roleplaying in general. If she hasn't before, that's great! Hopefully she gets to have some fun with something new. But it also means she needs to understand how it works in this context and how it might differ from other games. Mainly that this is first and foremost a group experience, so she shouldn't expect her character to necessarily have the spotlight all the time, and sometimes it might be necessary to forego exactly what she wants for her character in the interest of, you know, the whole group having fun.
3. She's gotta be committed to it! With seven players, it could conceivably take quite a while for everyone to get their post in and advance the plot. Which is fine, it just means she needs to be ready to go without dawdling all too much when it's her turn. (and I know I am biased on this since I usually like to speed post... so I defer to the rest of the crew on the specifics of this, but I think the point is essentially valid)
But yeah, if she's ok with all that, by all means! I'm not too concerned about exactly what class or character she decides to create (I like to think the character's backstory, personality, and individual perspective can be what they bring to the table, even if their skills aren't 100% unique ;) ), so whatever she thinks she'll enjoy playing. Looking forward to seeing her sheet!