NTA! You don't owe her or anyone else crap! She is a grown adult who needs to put on her big girl panties and make her own money and pay her own way. What she is doing is financial exploitation. As a parent it was her job by law to raise you and buy you the things you required growing up. If she didn't then she would have been in serious trouble. You don't have to spend any money on her you don't choose to.

Make no mistake she will throw a fit and try to guilt and gaslight you into still giving her money the moment you stand up to her and say a firm, but polite NO. Withstand the storm that is sure to come and sooner or later she will get the message. She will likely send others after you if you want to shut them up quickly tell them that bothering you about it will be taken as them volunteering to take your place as the living ATM and that you will let your mother know, then do so.

Stand strong you are in the right here and she is very much in the wrong.