How to deal with a friend who is a pathological liar.?

[Katelynn]

My best friend of 12 years just won't stop feeding me lies...

Back in July our friendship was put on hold, almost ended, because she was making up lies to several friends and a potential bf, she did this because she was jealous and wanted those friends all to her self...

As of December, we're friends again, but she won't even admit to or take responsibility of her actions... She's trying to convince me that someone hacked her FaceBook account, that whomever hacked it sent those lies and tried to ruin my relationships with other people, that she would never say those things. While telling me these lies, I showed obvious sings of disbelief, so she started making lies to cover up and keep pace with her other lies... I showed signs of disappointment, and after a while I told her I didn't want to talk about it... But I didn't know how to confront her... I wanted to say "stop lying to me, you're not fooling anyone. Why can't you admit to your actions?" but didn't want to scare her away and lose our relationship... I felt like she was trying to run away from the truth. She was so nervous, shaking even, like she was afraid of me.

She's always blaming every action on her bipolar one. She's 20, will be turning 21 in June.

I don't want to just end our friendship, we've been though so much together... She's like a sister to me, and I don't have any family besides my mother. But at the same time, I can't stand being lied to...

When we were younger I caught her trying to convince my bf (my ex) to sleep with her... Out of embarrassment, she went psycho... Grabbed a pair of scissors and tried to slit her wrists- I had to tackle her and take them away and proceeded to sit on top of her till she calmed down.

I'm afraid that if I don't make her admit to her actions, and I let her get away with it, that she'll do it again... Because this isn't the first, second, or third time this has happened. She has no regrets.
The lied she made up to my friends where about me. Like, telling them I weigh 500 pounds, that I'm nasty, just all sorts of things to make me look bad.