Most Helpful Girl
I say get rid of the girlfriend. You shouldn't have to choose between the 2...
Most Helpful Guy
I say you can do a few things
1st is you can try to understand her insecurity and reinforce it positively, I mean as I talk with her and try to find out why she's like that then reassure her she has nothing to fear.
2nd option is basically the same as the 1st with the change of that she's just generally not willing to be flexible and is just a straight through selfish or self centered person.
Lastly you can listen to everyone that says ditch her, learn nothing in the process and let her be someone else's problem. If the case is like number 1 where she's just insecure cause she's had bad experiences you could be the break in the cycle. If it's 2 and she's possessive then you can't change that but you know for sure.