Awwww, tiggy, you will know when it is time. Gaining weight is such a good sign so I think your vet is right, give her some more time. It will take a while for recovery.
My ex-boss had to feed her cat for almost 3 months and that was years ago and the kitty is still alive today.
Cat maid to:
Puddles, female Himalayan (16 yrs)
Jasper, male Ragdoll ?? (approx 9 yrs)
Sweet Pea, female silver tabby DSH (approx 7 yrs)
Rose semi feral, a cpietra rescue, female tabby (approx 6 yrs)
Snowball RIP (1991-2005)
In a cat's eye, all things belong to cats.-English Proverb
“While we are free to choose our actions, we are not free to choose the consequences of our actions.” Stephen R. Covey