I like how Alice let him enter with no hesitations. I mean, part of me wants to say that it's because she entered his mind and saw his deepest desires, even his DEEPEST desire without him entering, and so she thinks that it's only fair to return the favor. The other part of me wants to say that Alice loves the duke and trusts him so much that she'd just have no qualms and would used this chance to get closer.
It's meant to be a bit ambiguous as what
@Delfador said. I think the intention is that no one truly knows what Sharon is like, even her journal is a bit of a front to her true personality and each person saw a different side of her. We're unwinding this mystery just as the characters are.
@Iceblade20