Hey fellow cat owners, I'm looking for a bit of advice

My 11 yr old cat recently had six teeth removed and then developed an upset tummy from her post op anti inflammatories. Her gums have thankfully healed up perfectly but her stomach is a little dodgy still and the vet prescribed her probiotics and some antacids.

All she can eat is her favourite meal, Pollack fish. The vet said it was fine to feed her nothing but that for a few days until her tummy settles if it's all she can manage but try to get her back onto her regular wet cat food asap. We have tried mixing the fish with some fish flavoured cat food that she used to eat every day with no fuss, but she won't touch the fish if it's been mixed in with cat food whatsoever - even if it's just a tiny amount. I thought if we just left some cat food out and didn't give her any fish, she would give in and eat the cat food once the hunger took hold but she starved herself and brings up bile which the vet said she shouldn't get to that stage since it'll upset her tummy more.

She's been eating nothing but Pollack for about four days now. She's also ate scraps of chicken and bacon but she can't live off of those.

I'm looking for advice on how to get her back into her usual routine and keep the fish as a treat

Thanks