I agree with Cherry!!
For the most part, my bf is my bad influence. He loves to take me out to eat, and I always feel like I have to keep up with how much he's eating. And we always splurge....appetizer, salad or soup, entree AND dessert. Ugh, makes me sick thinking about it. For that reason, I'm glad we're living in separate states right now, so it doesn't happen as often! LoL
BUT...recently, I've got his butt going to the gym. He and his buddies are even doing the P90X thing. He says he's gonna burn me the dvd.
And I do have one girlfriend that's very weight-conscious, but makes terrible diet decisions---chocolate, ice cream, cookies...definitely has a sweet tooth! We get together and man, it's over! LoL BUT...I have her doing the 30DS with me.
I say just talk with your friend...or opt for healthier choices when you're with her...I know it'll take TONS of willpower, but maybe she'll follow suit!