New guinea pig owner has a question...

Hello, everyone. This is my first time posting to a guinea pig forum, as I am new to guinea pig ownership. We got our first baby girl, Molly, on March 7th. She was living a spoiled and lovely life, but as I read more about piggies, I realized we needed to get her a sister. So, we adopted baby girl number 2, Bridget, a few weeks later. We kept our new guinea pig quarantined and also took her to a guinea pig vet for complete check-up, just like we did for the first one. Everyone was healthy, so after 3 weeks we decided to introduce them today. We did our homework and made sure everything was set up appropriately.

Molly (she's our first one) nipped, chased and head butted Bridget (our baby). Bridget submitted to Molly every time. Molly is a bit older and bigger than Bridget. Neither of the girls ever chattered teeth. Four hours later, things died down and Molly showed no more aggressive behavior. They seemed to just sniff around everywhere. So, we set up their new, huge cage we ordered and put together, and put both girls in their new home. Now, we notice that Molly has started chasing Bridget again, nipping at her, basically not letting her go anywhere without chasing her away and nipping at her. My question is...how long do we allow this bullying behavior from Molly before taking action? I don't have any furniture in right now because Molly gives Bridget no peace.

Sorry so long. I know this is only day 1, but I just want to make sure we're doing everything right.