bah, she was just playing safe in the beginning. you can already tell by her enthusiasm that she's into you. but anyways, after careful analysis, these maybe be the factors that led to the desired outcome:
1. the moment she stepped out of the car, she felt guilt
2. she thought it over that she might regret it for the rest of her life denying you a chance
3. she figured that from all of her relationships that you are the most sincere
4. she doesn't want to be alone
5. she was in the state of self denial because she felt it wasn't right to get flattered easily primarily because of the fear of failing another relationship
6. she is suppressing her fire
7. all she ever wanted is to have an honest and functional relationship
8. she was initially generous in giving suitors some chances but grew cautious
9. she had an epiphany
10. bah, WTH! just go for it