if you are looking for a relationship and not just trying to have a good time with a pretty girl, i think one thing we forget is it takes about 3 seconds to "fall in love" according to movies, books, etc...."falling in love" according to these standards is nothing more than a chemical and learned reaction to what we find attractive...don't think because you like the answers she gave during a first meeting, even if it did last three hours, are anywhere near accurate...most try to put themselves forward in the best light possible which is understandable when trying to land someone as a partner
if you think, based on your original meeting, that there is something worth pursuing, take the time she has given you to get to know the real her and let her get to know the real you...the last thing you want to do is develop deeper feelings for someone you don't even know...what happens if you discover you don't like the real her if you have already jumped into a relationship before getting to truly know one another? hurt feelings, a "broken heart", and even more time suffering
a true relationship with a life companion takes a lifetime to create!
this girl you met may not be doing it on purpose (or she might, i have no idea) but developing shared history and letting you feel there is a bond, taking a couple days to let it set, than demonstrating that she has the power in the relationship by taking what you want (her) away is an old, old trick...men always want what they can't have and will strive to acquire whatever seems to be out of reach...that's just the way we are wired
like previously said, finding a prettier girl (even if she is just a friend also) to be seen with will work on a lot of females because they tend to be very competitive with each other and will judge themselves on whether or not they can take you attention from the other...at that point, it is crucial to be friendly, acknowledge her briefly, and go back to paying attention to the girl you are with...if you do any more, you give the girl you are trying to attract all of the power in the relationship again if she sees you dump whoever you are with just because she smiled at you...good luck