No, it is coded into the game for him to catch this ralts:
Because it evolves into Gallade and then Mega Evolves, the only way is for it to do this is to be a male Ralts.
Wally cannot catch a female Ralts at the beginning of ORAS. If it was somehow hacked to be a female Ralts it would probably change to a boy when you battle him.
Hope I helped!