You gotta remember my pimp character is a Redguard. I'm sure once she's hooked on moon sugar she'll lighten up.

As in making her consider you as a potential love interest? Nope, not a chance.

You can choose to always ask Serana if she's okay (that question comes up three times at different moments) if you want to be as nice as possible.

But ultimately, there are no consequences. Even if you try to be an [censored], like when Serana thanks you for getting her to the castle and you may answer "What now?" she still will like you (as a friend, of course).

The only difference is whether you'll get the option to have her cured or not, which is pointless because she clearly doesn't give a damn. You have to talk her into it.

Nah... Serana is never flirty, unless you are one of those who mistake being nice for coming on to you.