Accidental Pregnancy Help

Hello again, rat reddit! Posting again for my little sister. Back in December she adopted two little rat brothers and, due to a still unknown cause but we're thinking congenital illness, one of them tragically and suddenly passed away. For obvious reasons, we needed to get the remaining boy a friend to keep him stimulated and so happily welcomed a younger rat into the house. We did NOT want breeding to happen, and our current rat isnt fixed yet, so we made sure to get another boy. A few weeks ago the new rat and the original were introduced and they loved each other immediately! They were introduced well and allowed to visit and spend supervised time with each other over the course of two weeks yadda yadda our mom took care of the two now fully introduced rats while we were gone on a four day vacation and my sister just told me our HE is a SHE with visible nipples and a baby bump. The two are now separated in case there's any chance she's just full of soup but the chances are slim. What changed should we make? Behavioral changes? Hormones? Should we provide different food or bedding? Any advice appreciated, yes the babies will be safe and well cared for once born🐀