Why would there even be a main "Mom"? I haven't played this one yet so maybe something contradicts this, but you were presumably adopted into a family of poly lesbians. I suppose two parents might have had to be picked for birth-certificate purposes, but beyond that they'd all equally be your mother. If one of them actually is your biomom, it's probably Lawrence.
Viewing post in Actual Roommates 2 - Sorority Crash comments
By main "mom" I'm refering to the person you end up with if you dont got down the harem route. I could be misremembering, but if you chose like 1 person, dont you adopt V with whoever you chose in the end? In my playthrough of AR1, I remained faithful to the first love (cant remember her name for the life of me).
But in 2 its revealed that you ended up with the Fujikawa girl.