Feeling Kind Of Guilty, Due To My Decision

Please don't feel guilty. You did absolutely the right thing!!! The MIL IS a risk, even if she turns out to be negative in the next few days, she may still be a carrier.
Their family should also understand that keeping MIL with any one is a risk. It sounds like the MIL can take care of herself - so what's the problem in staying alone? Let her stay alone.
It is not worth risking others lives just because the MIL wants to live with someone.
DO NOT FEEL GUILTY. You are gutsy and stood up for your parents. That's admirable. If only more people had the same guts as you, we would not have so many Covid cases today!

 

Actually, they have to understand first not to bother anyone in this, as it is a virus, which may show up anytime depending on the exposure. If they dont understand what can we do? Telling the inconvenience straight is the best way. Or they should have asked for your consent first, whether it is OK for you all to send her. Since they dont have that decency, you need not feel guilty at all.
In case due to her stay if any of ur family member's immune system is so weak that they may get a chance for the virus what will you do? Anybody will simply say sorry. So what u did is correct.