It does sound likes shes suffering, in which case she needs to see a vet. Like stated, a vet wont suggest euthansia unless it really is the best thing to do.

You also need to be extremely careful about medicating you own animals. These drugs are prescription only for a reason. It may seem like vets have a standard approach (bayril, septrin, metacam) but they know what they are doing, and know that certain conditions can be exacerbated by certain drugs.

Metacam is certainly one that has to be used cautiously in small animals.