just need to know when to part my dogs?

don't want to be a breeder, she is too young to have pps at 7 month, 1 litter when she's 2 like the vet recommended, i don't want her to get caught so when do i part her from the dog to stop it? when she gets swollen or before? and how long do i need to keep them apart?

She shouldn't be close enough to ANY intact male dog to the point where you NEED to separate them. She doesn't need to be bred, not when she's 2, not ever. You obviously have no clue what you're doing and breeding a dog as small as yours is when you have no idea what you're doing can be dangerous.

Vets do not recommend litters at any age.

I answered when to separate them on your other question. However, dogs don't need to have one litter to be healthy. They're quite fine not having any puppies. It won't "make her a better dog", and if your vet is recommending you breed her, you need a different vet.It's also likely that she's not of good enough quality to breed, and you shouldn't breed her then. And if you don't want to be a breeder, why are you considering breeding her? there's no need :). There have been some studies that letting the dogs keep their sex parts until they're mature at the age of two can be healthy for them. However, after each heat, the stats for likelihood of cancer increases. Doesn't mean that your dog will get cancer, but the risk increases, as well as for a few other things (read up on it). Also, you'll have to deal with the hormone-induced changes, and watching her very carefully to make sure she doesn't mate during those heats. That can be be a very stressful and anxious time, so if you want to avoid that headache, spay her. If your reasons for not spaying her are that you want her to mature first, (which imo Is a valid reason) then have her spayed after her second heat, or around 2 years old. But there's no need to breed her.