Ok this is half-annoying and half-hilarious that she is bonkers.
MIL talks to my baby DS like her pet cat. "Who's a gorgeous boy? Who's a gorgeous boy? You are!" And whistles at him to get his attention (no idea why, it doesn't work).
We're staying at PILs at the moment. It's getting so ridiculous that I heard her going "who's a beautiful boy??? Would you like a cuddle?" in the next room and I assumed she was playing with DS (DH let me have a lie in). I sat up in bed and realised that DS was asleep next to me in his Moses basket and she was talking to her cat. 
AIBU to find this annoying but also hilarious proof she is getting old and dotty?