"Losing It," by Melodie Johnson Howe, in Ellery Queen's Mystery Magazine, August 2012.
But my friend Melodie made me a believer in this one, largely because the story is so twisty it makes a corkscrew look like a knitting needle.
Callie Taylor is the mouse in question, a manicurist. Mike is the boyfriend, supposedly working on a screenplay, but apparently only working on the groceries Callie brings home on her paycheck.
One night Callie rebels against her life by spending a thousand dollars she can't afford on a shawl. Mike hates it because it keeps her from looking "normal," the ordinary person he wants her to be.
And then, late one night in a bar, she loses the shawl. And worse, one of her wealthy customers shows up wearing the shawl - complete with the tears Mike's dog put in it. How can Callie get it back without losing her job?
That's where I have to stop, so as not to reveal any twists. Let's just say, whatever you think is going to happen, you're wrong.
But you'll have a very good time being wrong.