For the abnormal sleeping pattern and change in appetite, this could be her grieving. Gliders can take it hard when their cage mates die, just the same as we do. She could be craving your attention because she is lonely. The popping noise is normal. My gliders do it especially loud when they're sleeping. I call it snoring.
Now, for the pee problem, Im no expert but I don't think that is normal. Does she hiss while she is peeing? She could have a uti. This is what you need to ask your vet about. Tell the vet to test the pee and poo, have them check for uti, and parasites.