Well, she has to keep up her reputation for schoolgirl zaniness somehow! 
Personally, I imagine the triplets sneaking in to Stacie’s rooms, after she comes to live at Freudesheim (which is an obvious place for an eminent Oxford classicist to live, because of all the world class libraries on the Platz), because it’s soothing to be around someone who isn’t all down with the kids/an eternal CS girl.
I mean, Joey would be a total nightmare to the average teenager — bessie mates with all your teachers, churning out babies, following your school around Europe, nipping through the hedge in a lime green twinset and earphones all the time to put in her oar.
No wonder the triplets boarded, even though they lived next door!