I have never said this to anyone before about their parent, but I think you have tried hard enough to get her to stop in the past, but she continues anyway, not caring how much she hurts or embarrasses you. So I think that you should seriously consider saying to her that you don't want her there, her presence will ruin the experience for you, so if she turns up you will be going no contact with her - and don't give her a time limit, as far as she is considered she should believe it is permanent.
I would add to that, what no contact actually means ie. you will block her phone, block her on social media if you share any, return any snail mail unopened, not open the door to her if she turns up at your home, and last but not least, tell her that if she trys to get any family members - or friends - to intervene between the two of you, you will not talk to them about it either.
You sound lovely OP, you have been much kinder and more patient than I would have been! Because of your loveliness you will probably be very much against what I have suggested, but I honestly think that your mother sounds like she will only pay attention to drastic action from you.
Unfortunately, if she still turns up at your event then you will need to go through with your ultimatum, and if you know that you can't do that, then please don't say anything to her in the first place, because when it does eventually become to much for you - and I really believe that it will - you will not have any negotiating tools that she believes in. As long as you don't tell your mother, or anyone else who knows her (as at least one person who knows her cannot be trusted) then in your own mind you can have an initial first time limit on your no contact decision. I would suggest that your minimum time limit the first time is no shorter than 3 months, and no longer than 6 months, as long as she stops trying to change your mind after the first week or two.
If you do all of that, but after you are back in lowish contact to begin with, she starts back with her old tricks, then I think you would need to go NC for at least a year. I am in my 60's so I am very aware of time passing, I obviously don't know how old your Mother is, or what state of health she is in, but I know that you will want to take that into consideration when deciding the length of any no contact you decide upon.
Unless your Mother was an awful Mum when you were a child, then I doubt that you will want to go permanently NC, and hopefully your Mother will learn quite quickly to stop being so impossible to be around. As PP have said, I really do hope that you get to enjoy your performance.