Huge hugs xx
My dad had a 'catastrophic' stroke four years ago and it's an immensely frightening thing.
Dad was paralysed on his right side and had severe aphasia, he's now about 80% physically recovered, his speech has recovered (he even speaks fluent French again). His was a lucky recovery but it does happen.
Things I learned that may be of use:
His was the left side of the brain so his right side was affected. It meant he had aphasia.
Her sight may be affected too, dad could see in his right eye but couldn't process so he saw a lamp but his brain said it was a cat etc.
Aphasia means he knew what he wanted to say but it came out wrong (tea please became bobcat by the stream). This may be what they mean if they say speech is affected, we were not expecting it and it made it harder to deal with so ask if you don't understand things.
Sleep is massively important, dad still gets exhausted now.
Dad didn't really understand who we were at first but he knew we were important and our visits helped him loads. Even just sitting with him talking about what was in the newspaper was good.
Fight, fight, fight for a swallowing assessment if you think she needs or wants to eat. Dads was delayed for days and he immediately improved once his blood sugar went up.
Make sure the nurse/doctor can deal with stroke case. I had a nurse removed from dad's care rota as she was shouting at him, she thought he was deaf because he didn't respond to questions. She hadn't read his chart and he got upset and frustrated.
If your MIL cant speak initially and they don't supply a picture board bring one in. Dad was desperate to answer yes, no etc but had no way of doing it.
Don't lose hope, recovery is possible and dad is still improving now.
Sorry this is so long I just wanted to offer practical stuff, we were floored when it happened and information was key to our helping dad.
Xx