friend thinks i'm selfish, but won't talk to me and address the problem.?

she has never said anything to me, but i know our friendship isn't working. she never talks to me, she comes to my house and says nothing all night. she uses me for my money. she never tells me anything important, if we didn't have a third "best friend" in the group, i'm going to be honest, i would never have met her. my mom thinks i don't need someone like her in my life to bring me down and depress me.

ii asked the third friend what's going on; she reluctantly admitted that in the past she has said i'm selfish, and that i turn every conversation into one about me. while that was once true, i try not to do it anymore. but isn't it better than sitting in an awkward silence? this girl doesn't speak unless she absolutely has to. last week, she stayed at my house, and spent two hours on my laptop talking to her boyfriend and another friend on G-chat. I just sat there in silence on the other side of the computer....

i can't address the issue with this girl, she doesn't know that i know she doesn't actually like me, but this is ridiculous. i know we're going to lose touch over the summer, i'm going to live with my cousins abroad for the whole break. but i feel like something needs to be said before then. what can i say to her? i don't want to leave the third friend with a "sophie's choice"