Bit of brief background. I have 3.5yo DS with DH. MIL is definitely of the 'hands off' GP variety. Fine. Not the sort to be chatting to children or take any interest in what they're doing. Again fine.
Despite this backdrop, MIL, since I've known her, has repeatedly lamented how she'd like to her her GC more (DH also has 2 elder children). Until our DS was born, this was easy enough for her to say because DH has limited access to the children. We've offered MIL on many occasions (including before DS was born, and since) that she is free to do stuff with the children/take them out whatever if/when she wants. She has never taken up this offer (btw she is active and able-bodied and doesn't work).
But what is incredibly annoying is that increasingly, she is recognising that DS barely knows here. It has always been obvious to me that he would hardly know her. After all, to him, she's someone who he sees fairly infrequently and when he does, it's over a mealtime in either her house or our's, where the conversation is of an adult nature and tbh, fairly boring.
As I said, MIL has never taken us up on the offer of doing stuff with the children. The only 'together' time she is interested in is either inviting us all up for dinner, or coming down to our's for dinner. If this is what she wants, then fine, but why oh why does she then seem to complain that DS barely knows her 
.
So for example over dinner yesterday. She was talking about what she'd been doing, film she'd just seen, what did we want for xmas, etc. I mentioned DS had been to the theatre with nursery. She just said 'oh that's nice' and kept talking about adult stuff. Then I mentioned his part in the xmas play and that he was really excited about it. She said 'oh' and kept talking.
Actually in writing this, I think that maybe when she next says this I should say something - maybe that he would know her better if she spent some time getting to know him? But this is likely to cause issues with DH as he doesn't like to 'rock the boat'.