Ooft, fatal mistake not recognising a narcissist before you introduced her to other people in your life.
You feel she is in competition because she is.
That's what narcissists do.
She is not your friend. She is a deeply damaged person who has made you their competition. And narcissists... intend to destroy their competition. Piece by piece. And steal what they want from them. She won't share your friends, she'll take them.
You have 2 options, 1, let her and the whole friend group go. Cut of the whole limb before the fast acting poison in your toe, spreads. Or 2, back away temporarily and hope she targets someone else and they see what she is and abandon her too. Slowly regaining your friend group one by one that way.
There are pitfalls in the later as, if she hurts a friend of yours-they may blame you for bringing her into the fold. Also if she sees you've backed off, she may go nuclear on you.
There's then a third option I suppose but...it relies on your friends being good friends to you and willing to believe you straight up rather than give her 'benefit of the doubt'. Tell them - she's turning everything into a competition and you realise she's not a nice or, safe person. That's a huge risky move too unfortunately.