There was Gisele in the OS
Which was a long time ago when the writers didn't feel that Ash being attracted to girls was taboo. Nowadays we're lucky if he even expresses mild interest in girls at all. Serena will have her work cut out for her in my opinion. She'll have to catch Ash's attention and there's very few ways of doing that, although she did well with those macaroons that she baked for him before.