I wanted to seriously thank everyone for telling me I did the right thing by adopting both of them. I have problems with anxiety and I was feeling incredibly anxious about this because Lapis came from a house where she was being aggressive towards three other rats in a 10 gal aquarium... I was so worried about overwhelming her with two new friends instead of one.
But I went ahead and introduced everyone to each other and it went so well. Lapis hasn't shown any dominance at all, much less aggressive. Tatsumaki is the dominant one, she stands on top of Lapis just like she does with her sister and Lapis absolutely doesn't care at all lol. It confirmed my feelings that her cage and her habitat were major contributors as to why she was acting up. I have no idea if introductions would have went as well if I would have split up the sisters too.
So basically yeah I wanted to thank everyone for being there for me even though I didn't mention my anxiety disorder. They're in a cage together now and all snuggled up in the same tube and I'm so glad I'm able to give all three of these girls a better life.