I would first go and consult this matter with the principle before taking any actions of speaking with the parent and see what they say as naturally we cannot have a parent participation that affects the students learning and well being. I would simple tell her that their is no need for any volunteering.

I would go to my principal just to inform them of the situation and possibly get advice from them. But also just inform the parents that there is no need for volunteering at the moment.

Inform the parent that there is no event coming up that would need volunteers. Should one come up, figure out how many parents you want to volunteer and only allow that many and no extras. When they ask why they werent chosen to volunteer you can let them know there are only a certain number of volunteers per event and you want to give other parents opportunities to be in the class as well. I would inform admin on the situation and let them know you would rather them not volunteer in your class.

I would let the parent know that there is a high demand of parents wanting to volunteer each week and you want to be fair with each and every one of them so you are going to keep each at a 2 or 3 volunteer times max each. Then hopefully, you will be able to upkeep that claim and max out the other parents each at 3 times as well.

There are many ways to do this, including bring up the fact you thought she wasn't necessarily nice to the students and ask her to correct it in the future as a suggestion for the next time she does in fact volunteer.