friendship adivce

Hi mums and dads.

I apologise now for it being so long

I'm really stuck and I really don't know what to do. I don't want to bring it up with my circle of friends because their is nothing worse then feeling like you have to choose sides (which I don't want to happen) I also feel like a real b**ch even writing but I know if I don't say something soon I'll explode. So I would love for your advice on if I say something or drop the friendship.

I have a really close friend and we have been friends for 2 years. When we first met I was told be careful but cause she tends to lie. I put it aside because I figured I'd make my own opinion on her. I noticed a few white lies but thought nothing of it. Anyway the last year I have noticed the lies have become extremly bad. The last month has been the worst. The first one was when she point blank lied to me about my son. I asked him if he had done it and he said no. I said to him you know what happens when you lie and asked him again and he said no I looked at my friend and said did he do it or did u do it? In which she replied no I didn't do it. It must have been him. I yelled at him and sent him to his room. I then brought him out once she had left and spoke to him in a calm manner and said now .... when you lie i get cranky and he said but mummy it didn't do it I even seen her do it. Then he said look I can't even reach. (He couldn't reach what the lie was about) I felt so horrible as a mother that I had disciplined him and she blankly lie to my face and watched me tell him off and aloud him to be yelled at about lying. Anyway she came over a few days later and my son was playing up and before I could even say anything she went over the top of me and started abusing the crap out of him. To which I said don't you ever speak to my son like that. When you have kids of your own that might be except able to them but I'm his mother and you are not. She got upset and which I felt bad but felt their was need for her to parent him.
Then Just last week she slept with a good friend of mine. He told me they didn't wear a condom (he told me the morning after it happened.) I called her saying I really would hope she went after work and got the morning after pill. She told me she would straight after work. I felt uneasy about it and she came around 20 minutes after work ( i know her roster being managers of the same place) and I asked her if she got it she said yes but had to go to the hospital to get it (the hospital is 20 minutes there and back) not to mention it doesn't have a me pharmacy so she would have had to see a doctor. She point blank lied to me about it. What gets worse is about half an hour after the conversation she laughed, and I said what? and she said "I really want a baby and do you know I'm ovulating atm by my calender". I was horrified for my male friend (yes it takes two to tango)
Then I find out just the other day that she told a friend of ours that I slept with her ex and another female.
When I found out I tried so hard not to explode but went home and cried because their is no way I would ever do something like that. I was so mortified my friend would actually think I would do that to her.
I also have found out last night that she has been causing trouble between me and other friends I have recently introduced her to. I feel like im in high school with her trying to compete for friendship. If I was threatened by her making friends with my friends I wouldn't of introduced them but I wanted her to make new friends. Now I'm regretting it.
What do I do? Do I tell my friend about the morning after pill which he thinks she took. (she may or may not have) do I leave our friend ship behind ?or do I confront her about it?