My friend isn't talking much, I asked if something I said bothered her and she said "This isn't about you Eric." Not sure what she meant by that. Does she mean I'm selfish or I'm not the problem?

You asked if something you said bothered her, she said it isn't about you. In other words she's not upset by something you said or did, she's upset about something else that has nothing to do with you. If she wants to talk to you about it, she will.

Selfish may not be the word that's accurate, but insecure might fit. I suspect you have done this before, made someone's discomfort or upset about you. Take your friend at her word and don't take things so personally. In the future maybe inquire "what's wrong" instead of "did I do/say something wrong". Much more sympathetic and astute, and less insecure sounding.

Regardless don't push it, and maybe more will be revealed later if she cares to share.