As her friend, I think it is your obligation to keep her from making a fool of herself. I would want that from my best friend.
Just say, "Hey, head's up, some of the stuff you've been sending around just isn't true." and forward her the snopes link so she can read it for herself. Hopefully she'll be so embarrassed that she'll learn to check or stop herself when the urge to forward hits.
I hate this. My co-worker, who is on a really different side of the political spectrum always sends me offensive things and it's all opinion stuff, so there's no truth/ fiction factor. It's just offensive. She knows that I don't agree. I've tried rebutting point by point, but she finds that offensive. You'd think she'd quit.
AAAAAAAAAAAAAAARRRRRRRGGGGGGGG. I feel for you. But if the stuff isn't offensive, do give her a head's up, otherwise people will be saying rude things about her behind her back, which is a lot worse than being corrected by your BF.