Hi,
Is there any way you can take a break from being around her? It sounds like you are overwhelmed with her and maybe that is part of your problem.
We are all individuals. We all have talents, gifts, and abilities that others do not. You have things that you are good at and I am sure she does too. What is it about her that makes you feel you are not as good as she is?
I have another friend who is dealing with this EXACT same issue and I told him that he is just as good as his friends, regardless of what he thinks. It is all in his mind. His friends love him, and he is a super great person, probably the same as you.
I don't know you, but you need to stop worrying about what she is doing and start focusing on making yourself happy. If we continually compare what we don't have, what we did not get and what we can't do... we will never grow as people. Hopefully this helps a little! Good luck!