I'm not entirely sure I understand everything thats gone on between you two, but you said that you have a girlfriend and you also asked this other girl out...thats not okay!
I looked into a girls eye, she turned red and kept looking. She knew I had a girlfriend. Next morning I text her if we could meet, she replied with a rude text and said she hated to feel guilty. I asked her out but she kept making excuses. Why has she changed?
Why would any girl want to start a relationship with a guy who has proven he is willing to cheat on his current girlfriend?