It's not exactly normal but not normal doesn't mean wrong, it just means not what most people do. It's certainly not normal to have Einstien's intelligence--but that sure doesn't mean that he was bad for being that smart.

I see two reasonable explanations: Either it's just that it took that long for her to have enough trust to open up to something like that, or because she's testing the waters to see how you would feel about a repeat engagement, either just the two of them or perhaps a threesome.