It's your property, that you were renting out, cuz you wanted to rent it out.

You had no intention of selling. So her going ahead and finding a realtor and getting a bank loan for property that is not for sale is on her.

If she has a loan and a realtor they can find her something that is listed. If she can't afford things that are listed for sale that is too bad, so sad, but not on you.

You've told her "no". That is all you need to say. You can't block them cuz they are your renters. You need to text whoever is the renter, and tell them: I am not selling you the property. I will not respond to any further conversations about it. I expect rent on x.

I'd also look into finding new renters. Let them be til the end of the lease, but find new ones after. Don't renew. Let them know this. They overstepped.

This is on them, and not on you.

NTA