My in-laws are very independent and do not need much from us. Recently however my father-in-law has been hospitalized and will not be returning home for quite a while. My mother-in-law is getting lost,forgetting where she has put things and will even blame us for stealing things if she can not find them. This is also making my FIL very impatient to return home and may hinder his healing. We are not quite sure where to start in order to keep her safe. What can we do?
Once you have those, I would figure out what help your MIL needs. Obviously, she is not going to be able to be the caretaker for her husband when he comes home from the hospital. I would see who else is available. Check into having someone come into the home to help. Keep in mind that if your MIL does have dementia, it will progress and at some point, she can't be left unattended.
I think I might look into an assisted living facility that could take them both. Chances are your FIL does know about her condition, but has been covering for her.
You need also to start an ongoing conversation with FIL ' s doctors about what kind of care he will need when he's released. It would seem sensible to start making a plan for them to be placed in the same facility.
As mentioned above, getting poa for both of them is a key element. It won't allow you to force them to do anything they don't want to, but a medical poa will allow the doctor's and rehab places to talk to you.