You can hook up and date characters even if their sexuality doesn't match yours. All you need is to increase lust. Flirt brazenly always increases lust a little, even if they don't like you.
She's harder to conquer because of the chaste trait, but it's not impossible, she's even my sub in my save, lol.
Since you don't care about using cheats, remove the chaste trait from her and that will solve the problem. But if you really want to change her sexuality, use an online save editor.
Edit: I told you the wrong name for flirting that always increases lust, it's actually brazenly flirting.