Third Wheel? Need help!?

I been in a relationship for almost 7 months with my girl and she has a best friend which i dont mind hanging out with her. Everytime we go somewhere like an improv or club, she always comes along and we are trying to find her a boyfriend. I tried getting a boyfriend but she is very picky. I dont understand why she is so picky when she is not a super model herself. What should i do?