The friend getting with the girl at the end

His best friend acts like a simp for a girl for the entire movie,but that girl shows that she is attracted to the main character for the entire movie. She tries to sleep with him in almost a stalkerish way,but never manages to do it. She confesses that he is her dream since she was a kid,and that she now wants to realize that dream,etc. Then,at the end they reveal that the friend and her got together and had a baby. Well,if i was his friend i would never get with a woman like that. Who guarantees him that,as soon as the main character makes some sweet eyes to her again,she gets tempted to sleep with him again? They should have given him a better ending,making him end up with just a random woman and have a baby with her,but at least it would have been someone who didnt prove to be obsessed with someone else for the entire movie.