First off, the link for the appearence doesn't work unless you copy it and pasts it in the URL. But it doesn't really matter because it's the same as your Avatar. Also, it's usually a good idea to add information to your history BUT you probably should have kept the part about her sister being a witch a secret in the bio.... Not that anyone will hold it against you, but you kind-of just spoiled your own twist, lol! The final criticism I have is that I'm pretty certain that the sword you linked two isn't a saber. I could be wrong, but it looks more like some kind-of scimitar or cutlass or something? It's not a huge deal, but I'm pretty sure sabres are usually straight....
Anyways, now that all the minor gripes are out of the way, accepted! She seems like a good recognizable character who's transformation ability could be potentially used in quite a few intresting ways... like if someone was trying to clash their weapon with the saber, you could just turn it into dagger form and back to get around their attack. Also, I like how her history has a purpose for joining the DWMA, that's always a good thing. I'm not sure if you thought about it, but joining the DWMA could also allow her to find out where the witch is eventually instead of just going around asking about her.
Well, I think that's enough detail to have gone over for now. See you around!