What do you do if you've acted in a very stupid flirty way towards someone before, now you have seriously repented of it and just want their friendship but they will have nothing whatsoever to do with you and won't forgive you? (I am a Christian here!)  

 

It's really good that you have been able to recognise that how you previously behaved was wrong and that you have asked for God's forgiveness.  However, repenting of our sins does not mean that the consequences of those sins will be wiped away.  God will always forgive us if we come to him and repent, but this is not the case with people.  

You cannot force thus person to forgive you and shouldn't push the issue.  You should respect how this person is feeling right now.  You can hope and pray that in time this person will recognise how you respected them and understand that you really were sorry for how you behaved.