What to do about a clingy friend?

my best friend is pretty clingy. She really puts me on a pedestal to be her best friend for some reason. i'm pretty sure she has borderline personality disorder. but anyways, she always needs to hang out with me on weekend nights and if i don't go out, she gets offended. and if i'm away she's always calling and facebooking me. also, when she's grounded she has to call me and skype me. i kind of wish she had other friends that she felt as comfortable around because it starts to annoy me after awhile, but i can't tell her because she'd go crazy