I am 23 and my best friend is 29. At the beginning of 2013, I met my ex through my best friend which caused problems. At first all was good but as the relationship went on he became controlling & abusive, she tried to give me advice and told me to leave but I thought I knew best and that he loved me. I know now it’s ridiculous and he was taking the piss out of me because I was young. I learnt a lot about myself throughout that period.
She was always SO involved in my relationship and knew more about my relationship than I did! I would say I wasn’t still seeing him when I was and she would scream in my face, call me all sorts, she would drive past his house to see if my car was there and even used to tell my manager what was going off in my personal life with regards to the physical and emotional abuse I was going through - which made me the subject of office gossip. I ended up losing my job. I understand she came from a good place and felt I ignored her advice. I hold my hands up and say that I did lie about still seeing him, I was just terrified of her finding out. I now see I should have got a fucking back bone, told her to back off and him to jog on.
When I split with him, we became close again, did everything together, went to family events, we spent every weekend together. Now I’ve met the most incredible guy, he adores me as do I, we spend most evenings together and he truly makes me so happy. Around the same time my OH came along, my friend began to do things I disagreed with e.g. sleeping with married men. This has happened 5 times now with different men in relationships/married. I do not want to be a part of that or associate with someone who does such things. Now she has accused me of ditching her, said she never sees me anymore (I do, I always make an effort to see her twice a week) I’d respect her if she was in the same situation. In the four years I’ve known her, she’s never had a relationship.
Over Christmas we’d normally see each other a lot. This year I want to enjoy my first Christmas, in a happy, loving and committed relationship and she’s got very snotty with me, although i'll still see her! 
I recently had quite a large friendship group (who she introduced me to) however due to the affairs and sleeping with married men we’ve all drifted off, some have had babies, some in new relationships (like me) and some have just become distant with her.
I know OH and I may not last forever (hopefully it does!) but how do I make her understand that, this Christmas/New Year/Any other special occasion I will want to spend time with OH as it’ll be our first and I do love him and his company is better than being out drunk and cold!
My other friends understand this, just not my best friend! And why doesn’t she give other friends the grief she gives me?
How do I approach this and tell her to back off without upsetting her/losing her? She really has been there during some difficult times and I know her heart is in the right place but I feel like i'm 13 years old ffs! 