Tell her exactly how you feel about her, despite all her faults. The true definition of love is when you know everything about a person, you accept it, and you want to be with them regardless. But make it soft, make it gentle, don't come on too hard. Also, Valentines day is a special day. Do something nice.
Roses are great if things are progressing, but Daisies are better for a beginning type of thing.
See how things progress and make the call for yourself. Just make it a special day for both of you, if it happens. Dear Mr. Niceguy, I'm a virgin, my boyfriend is not. He tries to push the envelope a little farther every time. The last time I just had to tell him to stop.