My sister and I never talk and when we have to see each other, she acts like she's my BFF?

Especially in front of people... she just puts on a show. How do I deal with this? She's really mean and hypocritical, and I don't want to go along with the whole BFF charade b/c it's so fake (just like her!!). How do I make it obvious that i won't be treated like that without being too obvious? (Honesty doens't work on her... trust me I've tried... I've talked to her and told her I want to be closer and honest and that it hurts when she's liek that, and she doesn't care, then she starts going crazy acting like a victim drama queen and saying that OMG she's such a horrible sister... bottomline she's nuts!) And how do I make it clear to others the real nature of our relationship? Because she always tries to make it seem like we're perfect in front of people and that is sooo annoying!!!