The more they are around the person the more they act like them. What happens to a person the longer they are in a relationship and become infected with the significant others personality.
Poisonality noun ˈpȯi-zᵊn·na-lə-tē Toxic people whose personalities are adept at inducing negativity in others, esp. depression, inferiority, anxiety. People who are able to convince others that everything — including life itself — is meaningless.
My god! I spent an hour in the car listening to her spew about why the universe shouldn't even be here and that there's no point to anything. What a poisonality!