For example, two nights ago, she started by asking me was I her oldest granddaughters Mum? Easy enough, I confirmed I was. Then she asked me where I was when my daughter was born - I gave the name of the hospital. 'No' said Mil, 'Where were you when she was born'. I tried just saying in a bed, naming the town, just saying in hospital - Mil just kept saying, getting increasingly annoyed with me, 'NO - where were you'. I apologized for not understanding and asked her could she explain to me what she wanted to know - got told not to be stupid, and the question repeated. I tried distraction, and got accused of 'avoiding the issue' - and the question repeated. She followed me from the room, when I said I had things to do and we would discus it later, she just kept getting crosser, and was totally fixed on getting an 'answer' to this same damn question.
Hubby was eventually able to distract her, but it took time, and she was really upset and agitated.
This has now happened several times - either a situation similar to above, or she will maybe ask us to confirm what it was that such and such a person said or did when they were here 'this morning'. Only half the time I don't know who 'such and such a person is', and in nevery instance, nobody has visited anyway. Mil makes it clear that SHE knows what it was that was either said or done, and wants us to confirm it - but that's as much of a clue as we get. I've tried saying that its slipped my mind, and can she remind me - get told that I couldn't possibly forget something 'like that'. Tell her 'Sorry - I think I was making tea/in the loo when whatever it was was being said or done - and she will accuse me of lying, giving me exact descriptions of where I was sitting, ect - but not one clue as to what it was she expects me to remember and confirm. Even tried making something up - and she really blew after that because what I said was obviously (and not surprisingly) not what she 'remembered' being said or done 
Distraction, before she completely loses it, is only possible when both of us are here - no way can the person she is asking distract - believe me, we have tried
Its not like the endless repetition, where we get asked the same thing 20 times in a 15 minute space of time - that's just memory 'holes' and all we have to do is repeatedly answer, and she doesn't get upset - but these 'fixated' questions, that no matter how we try, are just impossible for us to answer, can lead to her having a real meltdown, paranoia kicking in, accusations of 'cruelty and messing with her head to drive her mad', tears and really obvious distress. And its only after she gets to this state, that we can then - perhaps - get her to 'let go' of the question that has caused all the trouble.
Has anyone else got experience of this? It seems to have begun at the same time as what we call 'invented history', to ourselves - she can give you incredibly detailed accounts of a completely invented conversation or event - and sometimes these questions come out of this 'invented history'. Although we have wondered if this is a form of 'provocation', if she is looking for an argument or reaction or attention, to be fair, she mostly just seems really frustrated and confused, and then -understandably, given that she can't work out why we 'won't answer' - she is angry Its really distressing for her - and not to nice for us to deal with, either
