I see a lot of arab in her. I had an arab QH/paint cross a year ago and she has the same movement he had. I see a lot of stock horse in her, too, but a lot of arab. It's quite possible she's a welsh mix- I've seen quite a few of those get mistaken for arabs around here when they're a more 'refined' strain of Welsh (a seller actually tried to pass one off as a purebred arab recently).
Honestly I wouldn't be too worried about what breed she is and if someone asks you just smile and proudly proclaim 'the best of both worlds' - she's definitely not pure so that would fly ^_^ very beautiful horse by the way.