well before, the whole point was that she had an ego just as big as Janns, took offense that.he "saved" her from thugs, and was hellbent on beating him to prove she was just as strong and didn't need saving. then in 5, they made her into Amy rose, creepy child stalker with a crush. again, nearly every characters characterization went down the drain with 5.
I'm not sure if every character's characterization went down the tubes by the time of 5, but more of Dimensions finally doing something Itagaki never bothered to do: Actually make the characters interact with each other past the elements in their rival battle.
And speaking of that, remember Ayane basically being touted as the villain in DOA2? Seriously, by how she was speaking and used, she could have easily became the final boss of DOA3 all on her own.
But back to my point, I do believe she always HAD that crush on Jann Lee, but it was more along the lines of proving she was his equal and gaining his respect and when she finally gained that at DOA4, THEN she basically played stalker. Although considering how Dimensions ruined Kasumi and Ayane beating Raidou and Genra by themselves due to BS, I usually take those parts out of canon.