MIL is now on her own and even though she has a house 2 hrs from us with guest room, MIL has decided she wants to make extended stays with different family members. She has no car and her DD, who lives near to us - DH's DS and my SIL, will have a newborn soon. SIL and her OH will have no guest room when LO arrives and ideally they don't want her staying at that time.
Ok we have space, and she thinks its more comfortable and convenient, but I think I will want to kill MIL if she stays here. MIL has a history of malicious gossip and snooping and she will try to get in here by only talking to DH - who will feel obliged because of his DS. DH and I have talked about it but did not really agree and left it undecided because I hate even talking about the subject. If this kind of visit happens even if we went away she would stay as long as she wanted and will search the house from top to bottom whenever we are out.
MIL would also get the house keys copied for herself which will mean changing three sets of locks yet again after she goes. We have stuff in the house which is confidential to our business, she will go through anything she likes given the chance on the pretext of 'cleaning'.
The risk of me thinking of murder comes from her total lack of respect or boundaries with anyone.
I'm always uncomfortable around her because I can't trust her and want to find a way to put her off trying to get herself in here. Even if she was in a B&B she would be round ours each morning before breakfast scrubbing the (fairly clean) skirting boards or something 
AIBU in trying to find some kind of an alternative?