Repression

Her Mom works nights so you take advantage of the fact you won't be disturbed. You and Jessica have a good time getting to know each other a little better, a lot better in fact.

Okay not THAT much better! Jessica may be a friend of your sister's, but she's not the "free spirit" she is. Jessica stops you from going any further and says she's just not ready to do that yet, especially since this is basically your first date!