My MIL is cripplingly hard work. She can be very interesting to talk to, particularly about art/the theatre, but she has the world's worst martyr complex ("I coulda been a contender but this random bad and unfair thing happened years ago and cost me my chance at X"), she never, ever listens and if she is not the centre of attention then she will either go out of her way to inconvenience you, ask a really awkward question or start an argument.
Sample convo:
MIL to DW: "Can I put my clothes in the washing machine with yours?" (Washing machine has been going a while)
DW: "There's not much point now, it's almost done, they won't get washed."
MIL: "But I wanted to wear these tomorrow."
DW: "That doesn't change the fact that they won't really have been washed properly if you put them in now".
MIL (sulking): "I'll do a later load then."
(comes over to me, looking at laundry basket with DD's stuff in)
MIL: "Maybe I can combine these clothes with my clothes later."
Me: "Sounds good"
MIL: "I just wanted to put my clothes in with DW's."
Me: "Yes, but they wouldn't have got clean."
MIL: "But I just thought I'd throw 'em in."
Me: "MIL, I see where you're coming from but your clothes won't get clean."
MIL: "But we'd planned to do our clothes in the same wash."
Me (losing patience): "Well, it looks like that didn't happen. What are you going to do about it?"
Another one from today:
DW (to me): How come your pyjamas are in the wash? I thought they were clean.
Me: I think they were just close to the rest of the stuff that was going to go in the wash, so I chucked them in.
MIL (shouting from the next room): Do you want me to find DD's pyjamas?
DW: I'm talking about DH's pyjamas, mum.
MIL: I could go look for you if you want.
DW: We're not talking about that, mum, this is DH's pyjamas.
MIL: Seriously, I'll go find them.
DW: Mum, that's NOT it. I can barely hear you from the other room either!
MIL: Have it your way. I was just trying to help.
Any five-minute silence will be filled with offers that sound lovely but in reality are logistically highly improbable (we have newborn twins, a 3 year old, and DW is the only driver in the house who can do anything more than very short trips):
MIL: You know, I was thinking of taking you all out to town for brunch. Wouldn't that be fabulous?
DW: That's a great offer but it'll be so hard to get everyone out of the house, and I have to tandem-breastfeed pretty much hourly right now.
MIL (displeased): Fine.
If you combine all this with the fact that she spends 4 hours of every other day freaking out about online law school and her computer not working and constantly calling "Brian from the technical department"... fuuuuuuuuuuu.
That said, she is great at doing all the chores for our older DD that we haven't had time for (cooking her meals, getting her dressed), so there's that to be grateful for. But by golly she is very, very trying.