Try not to be angry with her. I'm sure that annoying you or over stepping the mark is the last thing on her mind. I'm not sure you can necessarily assume that she is bitter that you don't want her to watch the kids.
Have you thought of slowly being honest with her. Clearly being subtle is not working. Ask her to scale back to visits? Or perhaps make the visits more mutually beneficial I.e. I see mums at swimming lesions who have a helper with them and I am always jealous! Or once a month she takes the kids for a walk or play whilst you do a big grocery shop? I know you have other people to 'call on' but why avoid her obvious desire to help and join in? Once a month is 12 times a year? Surely you can fit that in, especially if its mutually beneficial. Think of all the things she can teach your children, even if it is just that they are loved by many. If you start to look forward to her visits perhaps you will view her in a more positive frame.

Also, about the money. Do you want it? If you don't then you need to talk to her. Explain that you changed your mind. If she wants to support your children financially then perhaps she can set something up that doesn't involve you? Or perhaps she can sponsor a child on behalf of each of them? Something she can build on with the kids and teach them about other cultures and the lives of other children.

I don't know what you should do. I just wonder how I would feel if I was your aunt.