introducing new guinea pig

Question
I have five guinea pigs. Two females (scruffy and mo) live together with one of the females babies (two more females) who were born last week. The other is a female (peanut) who originally lived with the elder two. She was not bought at the same time and was about a month older. She gradually started bullying the younger of the pair, and then the other. When I discovered that Scruffy was pregnant (from before we brought her home), I removed peanut as I feared for the babies, as by now she was biting when bullying. Peanut now lives in a four foot long hutch on her own. I feel terrible to see her alone. I dont think she can be all that happy as she doesnt come out much and when she goes in her run on the grass, she doesnt run about. I was considering trying another young female guinea pig to go in with scruffy (she is now about 5-6 months old). Would this be possible or do you think she will be likely to still bully her? If it would be possible what age would you suggest buying?
Thankyou for your time.
Louise

Answer
Chances are the cage was not big enough for the two of them, it was just dominance, or the other sow was in heat.

I don't suggest buying at all, instead look for a cavy rescue or cavies in shetlers needing good homes.
www.petfinder.com
www.cavyrescue.com