RG - it's a tricky one isn't it? I think your solution is best. Could MIL have her for a couple of hours each week on a day you don't work to make up the hours she feels she's missing out on? That way you could have some me time. 12 hours is a very long time for anyone to spend with an energetic 3 year old, let alone an older person. My ILs are miles away so they always feel like they have to spend every waking minute with the kids when they visit, or when we visit them, and sometimes the kids disappear to a bit of space as they can be a bit suffocating! I think they also feel that my parents must get loads more time with them, when in fact they don't, especially since Dad's been in hospital since the end of Feb. Mum works full time and visits Dad on Saturdays, her rest time on a Sunday is valuable to her so I always ensure when we do visit that we don't overstay our welcome, I can't have her being ill too!
Greedy - back to work bootcamp might be necessary here - I baked 44 mini muffins today as I had a friend coming for coffee. Needless to say, there are 44 now!
Speaking of Dad, he's doing a home visit tomorrow, and Mum is going to bring him here for a bit too. It'll be only his 2nd time home since February, and this is going to be a gradual process, but it's moving in the right direction. He's going through a phase of making lists at the moment and phoned me at 6:50 am last Tuesday to ask for some birthdays of various relatives. He doesn't have much concept of time at the the moment and gets confused between morning and evening 
DD's 6th birthday on Thursday, and GCSE results day so she's got the special treat of coming to work with me! She was actually born on results day, I remember asking the registrar who was stitching me up in theatre if I would make it into work that day to see my pupils! I think the drugs may have got to me
. I'm probably as nervous as my students, maybe even more so!
Hope you're having lovely weather, Loopy!