Has this ever happen with you pet?

I've had my dog melody a mini pin for 6 years she has alway slept with my girls. But last night my 4 year old pooped her pants but didn't wake up and let me know and 2 am she said she had to go potty when I took her I saw her brand new panties had a hole chewed in then. Melody didn't evn wake her up when she ate her underwear off her and cleaned her butt. This is the nastiest thing I have ever heard of I can only think that melody who has had puppies before was just tring to clean her up like she was her puppy or something its never ever happened before. I don't know if I'm going to let melody sleep in there with the girls again but its going to break my oldest daughter heart she never sleep without her. Am I overreaction? Has anybody else dog done anything like this?