One of them suffers from schizophrenia and refuses to take her meds. The other has been diagnosed with a delusional disorder that made her believe in Slender Man. I would say they are a looney combo.
In the past, the parents would simply intervene, and say Sally, you cannot call or visit Jean anymore. Jean get’s you both into trouble. Now, it’s difficult to make that order stick with texting, skyping, emails and snapchat available.