In the storeroom before the latest update, I remember that you could find a machine that would give you a power boost of sorts, then you could choose Alice or Michael to get in the machine and get a boost before the machine died forever. I ended up choosing Michael, but I'm curious, if I chose Alice would she still have become a monster in the colosseum fight against Danu? BTW, sorry for the literal paragraph.
The update was 2 month ago, so my memory is a bit hazy. To answer ur question, it does not matter. She will be monsterified. Alice and Michaels powerup flags are not used as of yet as much as I know.
edit: also, with us empowering them like that, we probably will see there solo battles at some point(but this is my speculation only).