new female

Question
I recently acquired a new female guinea pig, nobody I talked to knew her exact age, although they had been taking care of her for about 5 weeks and their breeder usually sends them babies when they are between 6-8 weeks old. She does not seem like she is only 3 1/2 months old though, she is as big as my other female who is 3 yrs, granted my other girl is small but still. Anyways I'm wondering, if she is older than they say, is she still young enough to breed? And is there any way to know for sure that it is safe for her?

Answer
To be honest i would not recommend breeding from a sow if you are not sure of its age and background
Breeding too old or too young could result in the death of the sow and/or her litter.
Also not knowing its genetics could result in  deformities, problems giving birth and internal problems

It is advise to mate her at about 6 months of age for a safe pregnancy and no later than 9-10 months for the first litter as long as you can find out her true age from the breeder