Does my dog have pyomentra?

I made the decision to have my dog spayed after her heat was over (was told I would have to wait til in-between heats to lessen risk of bleeding) her heat seemed to go on forever but the bleeding stopped a couple day ago so I was expecting her to be out of heat completely rather soon. But today I noticed that she has a clear White discharge with a yellow tint to it. I've started freaking out and phoned the emergency vet, they asked me loads of questions about her behaviour and eating and drinking habits, all seem normal to me. She's not drinking excessively, eating normally and is bouncy and active. So they said to me that it's probably ok and to bring her in first thing in the morning to be checked. But in not so sure it's ok, I'm really getting scared, especially since I found out the price of getting a dog spayed with pyo! This week was meant to be sorting out everything, her spaying and insurance and this has happened. If she has pyo, and the price is incredibly high, I can't afford it. I'm terrified. I wished I had done the spaying a few months ago in like march rather than waiting til august. Has anyone got the lowdown on how much spaying a dog with pyo in the uk would cost? Not anywhere else only uk. It might not be pyo cuz I hear it occurs a few weeks after the heat, well she only stopped bleeding like 2days ago, Shes still swollen. Maybe I'm mistaking the fluid for pus when it's just discharge after the bloody show? Worst mistake ever was not getting her spayed sooner. Shes 3 btw.