I feel the reason for Alice's outlook is that because of the situation which she was in at the time of her turning, she doesn't dwell on her lost human years. Alice is happy with what she has and in the fact that she has found her soul mate and has a loving family. She has all the things she needs to be happy. Whereas the rest all have their issues with what they are or issues in that they do not yet have a soul mate. Alice still has some issues with her past, but she has what she needs to be happy. Even when she is unhappy, it is for only a moment in time, not something that drags on for eons.