Have you had any romantic interactions with her at all in any act? If not, I doubt you’re getting frisky with her starting in act 3, but I could be wrong.
I told her I'd look for night orchids and also made a move at the Grove celebration but I didn't have enough approval. I assumed there would be more opportunities. I wish the game would tell you that it's necessary in act 1 because from what I've seen a lot of people missed it.