Why does my sister lie like this?

I could use some advice on how to deal with my sister. She makes up stories all the time! I guess it is for attention, but we can't ever just hang out like friends because she wants to have a lot of drama going on. She started posting pics of herself on myspace, leaving hints that she's pregnant--but she's not--she just likes the attention. But our dad found out, and he doesn't know whether to believe the stuff she wrote or not, and doesn't want to ask her because she will make something up. Neither of us live with him. My sister lives with grandparents and they'll freak out if they know she is making up stories like that still.

How old is your sister again?

lol id advise ignoring it, I think all teenage sisters are like this

Dear octobersun,
Well giving the living situation we will assume there has been some trouble within the family. Your sister is telling everyone she needs some help. She may be very confused about her life at the moment. Perhaps you could talk with your dad/mom about having her see a school counsellor. They can asses her and maybe recommend her to see a counsellor outside the school who is better able to deal with this type of situation. She's trying to tell you all something...you're listen is everyone else?
Sue...good luck

She's 19, but not mature (I mean, I'm younger, but I'd never do the stuff she does). She's lived with my grandparents most of her life...we are half sisters. She's just so werid.

if she is 19 and acting like that I would wondered...she probably does want all the attention she can get...trust I have 4 sisters I know this...