My friend has no other friends!?

[Just Sayin]

Okay, I'm a girl and I have this on friend who has no other friends but me and and this other girl. She seriously has no one else to sit with at our entire high school but me or the other girl. My friend facebook messages lots of boys from other near by highschools but they never have met each other or barely see each other. I sometimes wonder what she texts/messages them, I think it's strange...

Anyway, I always feel like I have to be the person she sits with or hangs out with. I feel almost trapped because I have other people from sports teams and just classes that I'd like to sit with at like that's say lunch but I can't because of her.

She'll really nice and I like her for a friend, but what should I do?