I asked her about curing her vamp problem and she told me not after what she went through to get it. So we decided to drop the subject. She kind of hinted at what Molag Bol did and it didn't sound very nice.
Dont talk to her about it til you finish the mission, then after its done, you can cure her. Otherwise she wont. I'd recommend not doing it, honestly. I like having the choice available if I ever wish to, or if they let us marry her (yea, right), but I dont because nothing changes except the eyes, which still glow and look supernatural, but arent the vamp eyes. She still complains about the sun, still uses vampire drain, still can use harkons sword, and still wears the hood. Not worth me losing those wonderful eyes.