not a dumb question at all! They are "girlfriends" (groomer x victim), as Katie lured Phoebe into running away to "move in" to her studio apartment. They met through a roblox discord server, one of the many places Katie prowled for vunerable targets.
Phoebe's officially missing and she's several states away from her home and family.
I've yet to really flesh out their backstory so i totally understand the confusion, lol!! thanks for the ask!