This happened to my Dad when he was in hospital after being run over. I went to visit him and found him acting in a most bizarre way, telling me that they were coming after him, and saying things like 'Watch out, he's got a gun'. I spoke to a nurse who eventually found me a doctor to speak to, I explained my concerns and he said 'well of course, he is senile!!' I was furious, and said that my Dad was far from senile, and that something else must be going on. This particular doctor continued to try and brush me off, so in the end, I demanded to see a different doctor, who having listened to what I had to say, said he would check the drugs he was taking, and to leave it with him for a few hours, and then go back. I went back and Dad was totally back to normal. I was horrified that just because he was in his 70's, a doctor could just jump to the conclusion that he was senile, and not want to look any further for causes of strange behaviour, in spite of being told that my Dad was normally as sane as I was.
Speak to the nursing staff, and tell them that your Mum isn't normally like this, and you want it investigating OP.