She probably thought it would be very rude to react in a truthful way. I've been through those situations sooo many times, and probably even more then I currently realized, looking back on the past. Often times, people will react in pleasant ways when there really thinking differently, why?, cause its the polite, NT thing to do. Sometimes, they may show certain subtlties on there faces indicating something else. If you do notice this then simply drop the subject. Often times, they might cover things up soo well that you cant tell. So thats a really tricky situation.
I once had a friend who I became rathe suspicious of so I even confronted her about certain issues, but she denied, denied, denied just because she just couldnt admit the truth because she just couldnt break the niceness. Some people are like that. You have to pay very close attention to a lot of crap that us aspies often overlook.