Goodness you should not be breeding guinea pigs since you know so little about them. Breeding guinea pigs is a very touchy situation and filled with difficulties and death. Being with a male for a week will not affect her weight in the manner you are thinking, if it were to affect it at all in a week it would be she would have lost a bit of weight trying to get away from him as she is not in heat and was trying to get away from his advances when peeing in his face did not work.
She will not start to gain weight to the point you will notice it until she is 40 to 45 days pregnant and then it will be like she is a bag of popcorn in the microwave! You will actually think you can see her getting bigger and bigger as you watch her. She will get huge if she carry's a large litter.
My Poor Miya is a smaller guinea pig and she had 5 pups! She litterer was wider then she was long. My daughter bough my grandchildren over to visit her and when she saw her she started to cry for her, she felt so sorry for how bad she had to feel.
S any way if your guinea pig is pregnant to the point she is putting on a lot of weight it will have nothing to do with last week with the male, trust me. Please reconsider breeding your females, if every thing is perfect you are looking at a 20% chance of the sow dieing of pregnancy related problems or during the birth of the pups. If the sow is bred to young or to old for the first time you are pushing that number as high as 80%.
I rescued two pregnant females and both pregnancy cost me over %500.00, do you have that kind of money laying around, the money was only small part of it,, the one sow had to be hand fed every 4 hours around the clock for 14 days, as well as 2 of her pups that lived, only for the first week they needed to be fed every 2 hours around the clock, and I did not have anyone to help me.It can and is a lot of work, it is not all fun and games with a bunch of adorable babies running about, Trust me.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.