Why would a guy treat a girl he loves like this while going out with someone else?

I understand your trouble in getting answers from Yahoo Answers sometimes, well there are just too many qns and perhaps it gets missed out.. well from my interpretation, this guy is really shy and he has a kind of inferiority complex that perhaps he's not good enough for her and he's not strong enough to ask Jane out. As for his girlfriend, he probably does like her but perhaps not so much as a girlfriend. She may be a substitution that is available for him to treat as Jane, due to the fact that perhaps they were already good friends before, but their relationship to him is purely platonic. Hope this helps.