I don't think a girl will ever FORGET that you were an AFC. Their perception of you is cemented straight away, it's like how first impressions take seconds to form. Once you have it in your head that somebody is a certain way it takes an awful lot of effort to change that perception. Think about your dad, most of us think of him as the strong saviour type, it took me years to realise that this was not the case, and he was in fact just a man.
If you were to go away for a while, and then come back, the person would see the change in you from when you left, but they would still remember you as that AFC, and only by showing them how you have changed would their idea of you change, if you do not show them your improvement, they still hold on to the idea of you as a AFC.
Over summer I saw some people I used to go to school with who I have not seen in 3/4 years, they recognised the physical change in me immediately, but still referred back to the AFCness of the old me. By the end of the conversation however they verbally expressed how much I had changed, because I had shown them through my words and actions that I am no longer a chump. In my absence from them I had changed, but when they saw me again they saw the old me, until I proved otherwise.
While going away for a period and coming back different is one aspect, when you are changing around people you see frequently the dynamic works a little differently. An example I can give is that last term I went to every single one of my lectures. I had resolved last year to take my education more seriously and had slowly been getting better attendance. The people that I met throughout last term saw me as a good student with a good workethic, however the people that have known me longer say it is 'out of character' for me and were surprised. They cannot see how I have changed because the change has been so gradual. Instead they still see me as the guy I used to be. The only way I will be able to win them around is by consistently being this 'new' person around them until they finally realise the change themselves. In time they will realise this change, however they will never forget how I used to be. When reminiscing it will always be mentioned how I used to be 'so lazy' or 'useless with girls', but because I have changed they will say 'and look at you now'.
I think this is a good thing though. I would want people to remember the old me, for it reflects well on me now.
And yes this does work for girls. A girl I lived with in first year is now interested in me. She used to tell me all the time about how nice I was, however now, she says that there is something different about me, I'm still nice in her head, but different; and she digs it.
Gunner