I'm concern about my friend?

She has all these online friends, a **** load of them. She isn't popular in school, and the only real friends she has is me and my other best friend. We feel bad for her and we try our best to make her feel better. But she talks to them, and it's creeping me out. She's 24/7 on the computer, she has there numbers, and theres this girl who she has on facebook and they act like sisters, but that girl in like 19 while she's 16. She's pushing us away, in shorter words she picked them over us. /: I find that wrong. Should I mind my own business? She just never leaves her house ... I'm worried that's all...