Put Jessica on over your Trish suit

Your guess is that by putting on the Jessica suit, becoming Jessica, and using the brown pen on your new Jessica body, you'll have the memories of both the real Jessica and whoever is wearing her. Maybe you'll be able to take off only a Jessica skin and become whoever was wearing Jessica, then take him or her off. You start getting into Jess, your relatively big Trish feet shrinking into Jessica's dainty ones. But maybe you shouldn't wear Jessica over Trish?