<human>: Can you provide a brief overview of the text?

I'll try to be concise. When we first started dating about 9 months ago, I hardly saw her old school friends (including her best friend) and we usually hung with our great mutual friends or just with each other. I had no issue with her old friends or her best friend, until she broke up with her boyfriend and moved in with my GF and her mum (didn't want to move in with family or stay living with her BF).
Long story short, the best friend is very friendly and bubbly, but on the inside she is shallow, vain and quite selfish. And has been living with my GF for the past 3-4 months, and I'm at my wits end.  
  
Because we spend less time together due to work/uni, she sees her best friend all the time at home and her awful mannerisms and opinions rub off onto my girlfriend and I begin to get turned off by her. Doing/saying things that aren't herself and it makes me so mad (not at her, just the friend).  
  
Anyway, the friend is pissing off to another city soon to live (thank god), and being the selfish brat she is, has done things a selfish brat would do when they won't have any obligations here anymore, such as: leaving her car for my GF to sell when she leaves instead of dealing with it herself (my GF is VERY busy), started sleeping with one of her friends (who now has feelings for her) even though she's leaving... The selfish behaviour never ends really.  

Anyway, the point of my story is that I want to hear about others' experiences where you couldn't stand or even hated you SO's best friend, and how things worked out for you guys (did you tell your SO how you feel or just endure the times you had to see the friend?).
Would love any advice too, its a really awkward position to be in if you've found yourself in something similar!
<bot>: Hate my girlfriend's best friend, she's a shallow, selfish person with whom I have nothing in common. Share your stories!