I used to get on very well with my MIL.......... until DH & I had children. She used to like to come and stay and has always treated our house as her own (sometimes a little too much!)
Turns out she was 'grooming' me to become her carer in her later years, she started dropping hints about moving nearer to us and how her friend had sold her house and her daughter and husband had built an annexe onto their house for her to live in with its own front door, with access to and from main house and what a good idea that was, perhaps we could do that. What made her think I would favour her above my own parents is beyond me. DH fortunately was horrified at the thought of her having a 'granny flat', and said it is hardly fair and we cant offer to do that for one parent without the other so that was never going to be a flyer.
She had assumed that I was going to be a 'career girl' and we would not have children, so her response when told she was going to be a grandmother was to say 'Oh' and follow it with a Queen Victoria expression of 'we are not amused' and a catsbum mouth. And since then her behaviour towards me is like that of a naughty child.
There have been many incidents like this down the years, but I just let it wash over me now, things like she will kiss everyone else goodbye when we leave after visiting her, but not me. I answered the phone when she rang and chatted with her for a bit, then said I would get DH to come to the phone, she said not to bother as there was nothing important and she had chatted to me so she knew all was well. Next time she rang, he answered and she told him I wouldnt let her speak to him!!
Never mind - at least I will know what not to do when I am a MIL!! 