Please believe us when we say that you have nothing to feel guilty about. You are such a dedicated rat mama. Some rats with PT go downhill really fast. The tumour doesn't respond to Pred, and all you can do is comfort them and make sure they are cared for in their last days. It's fortunate that she is sleeping and not in pain... but such a big shock for you and your family to see her health deteriorate so quickly.
I remember SQ's Lois, who was an adventurous and energetic girl until a few days before she died. She was suddenly less active, then she couldn't eat solids, then two days later she died. I don't think she was fully conscious for the last day of her life. So fast. It was merciful for Lois, but very hard on everyone who loved her.
I am sad to think of the contrast between the way I remember Sydney and the way she is now. Please give her a pat and a kiss for me.