Can I tell my ex that how much I spend is none of her business.
Why does your ex care about how much you spend?
She's still trying to control my life and my spending even though we're not dating anymore.
I'm sure it's very frustrating for you to have your ex tell you what to do. You should tell her that since you are not dating, it's none of her business how you spend your money. Be as direct with her as possible.
She doesn't like me spending money on other girls.
Well that is understandable, but at the end of the day it sounds like this relationship is not going to work. You need to talk to her and tell her that it's over.