I'm so sorry you're going through this with Gertrude, I agree this sounds like an obstruction of some sort. She may have eaten something she found that you don't know about. The best thing is to have a vet assess her to be safe. My Dozer loves to eat sweat socks and has done so on 4 occasions. Each time he was able to either throw it up, or poop it out, but he did show signs of obstruction on one occasion. We took him to the vet and they did an X-ray, gave him a laxative and sent him home for us to observe. He did pass the sock later that night. The signs of obstruction to watch for are drooling water from the mouth, vomiting, a d or diarrhea, and lethargy. I hope Gertrude is okay, and feels better soon. Please keep us updated on what the vet says. Sending love, hugs and prayers.