I've had my problems with her. She can be very emotionally draining - I think she has suffered with depression in the past but being 'old school' just soldiered on without help. She lacks self-confidence and TBH had a dreadful childhood. I spent years just feeling sorry for her and protective of her...and then years cross with her because I didn't want to have to feel protective of her! Over the years since DS1 was born there have been times when I have wanted to stop her seeing the DC - nasty snippy comments and little niggles (about them and me as their parent). But I didn't and by and large we all rubbed along together and the children are fond of her (but aware of her foibles).
But then the other night she rang up to discuss christmas and out of the blue said "Thankyou for letting us share your children". it seemed to sum up everything I would have wanted her to feel and worried that she didn't.