CASUAL SEX : CAN IT BEGIN A RELATIONSHIP?

I know that this topic is one that is being talked about a lot but than also i want to talk about it as one of my friend told me one incident which i want to share with you guys and want to know what you think about it.Here we go......

My friend was chatting online on yahoo messenger and he came across an unknown girl who told her age 25 years.They did usual chatting.Then my friend asked her phone number which she refused to gave instead she asked his number and he gave it.After three days the girl called him when he was in college.They talked normally,hello.. hi.. how are you?? stuff..then suddenly after knowing that she is alone in her house he said that he is coming.....and he went... obviously with a pack of condoms as they both believed in safe sex.

He reached her street, she was standing there to escort him up to her flat...they went in.For the first half hour or so they both just had normal conversation about each other their past,present and a bit future.. After sometime the moment arrived and they did it...not once or twice but thrice.They stopped after third as they didn't had more condoms.

After it was all over, the girl escorted my friend to the same point at which they first met.She said that it was a good experience.....as my friend was a virgin till that time.... but this is for the first and last time that they see each other and she left.Till date my friend had no contact with that girl.

I have one question in my mind that why she said that they both will not meet again as they both did it out of their own free wish and will so why they cant meet again? Was she afraid that if they do so than they will get into an emotional relationship which she feared?? Was she afraid of commitment??? I really have no answers to these mysterious questions of mine.Do you have?
Please send me your comments at avijitkhanwilkar@yahoo.com or avijitkhanwilkar@gmail.com