I'm gonna agree with iduguphergrave, on Hanners not wanting to leave because she didn't know when Faye or Padma would return. It would be as though one of your friends suddenly got up to run to their house and get something. You know they're returning, but you don't know when, so you're faced with a choice: go after them, which would be kinda weird (after all, they could be coming right back, in which case you look really clingy), or wait there until they return, which is what Hanners did.
It really makes sense when you consider Hanner's tendency to over analyze, and the behaviors of people with social anxiety. If put in the same spot, I'd probably wait right there for awhile, seeing if they came back, before I'd text/call. Someone with severe anxiety might not want to even do that, for fear their friends would think them too clingy.