That was your final warning.
The in-laws are here, and the boundary violations have begun.
Sample 1. Its bedtime. A is on call. Mother-in-law tells sister-in-law, 'Sleep with P if you're scared, since A is not here.'
1. She is 27, for eff's sake. If she is scared of sleeping by herself, take her to a shrink. (On second thoughts, maybe not.)
2. This is my bed, you know. Does it even vaguely cross your mind that I may not want to share my conjugal bed with my husband's sister? Does it even vaguely occur to you to ask?
I'd give you sample 2, but its too depressing. Have a great weekend.