Most Helpful Girl
Aside from insecurity and using a boyfriend to justify feeling good about themselves, sometimes girls ACTUALLY appreciate their partners lol.
But yes, you're right, a lot of the time, relationships are security blankets for girls. I think there is nothing wrong with being friends with a girl, seeing how your personalities match, etc. as long as there is no cheating considered. Draw a very firm line between friends and taking the next step (if you get there). If you actually want things to work out for more than one or two makeout sessions, you need to make it clear that you won't consider going behind anyone's back to be with her. Respecting her boyfriend (even if she doesn't seem to) and that will go a long way in making you seem like a good option...maybe good enough that she'd consider switching relationships.