It's a Dog's Life

I came in from outside to hear my dog whimpering in the downstairs toilet with the door shut so I opened the door to let her out just as M-I-L walked into the room.

I said "Why did you shut her in there?"

M-I-L denied all knowledge of it, despite the fact that there was only she and I in the house.
When I pointed out that I hadn't done it she said that she'd been in there about five minutes ago and had definitely left the door open so the dog must have gone in and shut the door herself.

I felt I should point out the obvious that the dog would have to have pulled the door behind her to shut it as it opens outwards.

M-I-L's response? She suggested that the dog must have pulled the door shut with her tail!

…must…stay…calm...