As Karen said, as long as Zazou can still find joy in her daily routines, there's nothing wrong with leaving her be and loving her as much as you do.
I think these are the hardest moments living with a beloved pet. No matter what, there is always guilt involved, and talking to the vet and other pet parents can be helpful.
It is important though to assess your own comfort level even if Zazou still seems to be enjoying life.
Does it bother you to see her like this... The exact right moment can never be known.