While I agree with the outcome just a bit of a tweak on your interaction with her.
You said:
"I basically told her that they probably needed to find another place and that it was very disrespectful to my already hurt feelings to have her mom try to do that. I told her that my S and BI did not want to be involved in any way shape or form so don't bother asking again."
What you should have said:
"I basically told her that they (no probably) needed to find another place."
Stop there! No need to explain your feelings, that was completely implied in your S and BIL silence, and on your continuing to hold firm.
If she continued to push then "I told her that my S and BI did not want to be involved in any way shape or form so don't bother asking again." would have been fine.
LANE, are you the one to end these conversations? You should be. Don't let them linger on longer than they should.
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018