Except she didn't train, that was one of the weird things about it. She simply found herself manifesting her psychic knives (Still the most insane self imposed limitation I've come across like that) and then a psi-katana... I think they eventually put it down to the merge with Revanche who had some skill with a sword, but the form of Betsy's powers has about as much to do with chi as Dazzler's light beams do.