Maybe she's a virgin and she's only willing to give a little kiss when she's drunk, even though she sounds cocky during the day to save appearances next to all the horny companions.
No, the OP has a good point about Shadowheart. Trust is generally an important element for a healthy romance, and Shadowheart is the type of character who needs to trust someone before she... "opens" up to them, since she does not remember anything about herself.
