I would say no. You can't really go by weight, especially when the females are still growing. My females are around 40g when they are not pregnant, almost 50g when they are. The 16g girl is definitely not pregnant. She probably won't conceive until she reaches a higher weight. None of my mice have become pregnant until they had already reached 25g or more. And that was them controlling it, not me. (I placed several 16-20g females in with a male and none became pregnant until they were well above 25g) Also, a pregnant mouse will only get the "ping-pong ball" effect when she is in her 3rd week of pregnancy.
With the other pregnant female, give her own place. Its free baby mice! I always keep pregnant mice I get from the store.
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