Miss Laura,
I'm so sorry your friends have let you down. This may sound like a dumb question, but is it possible they communicate with everyone that way on facebook? I know when I'm trying to talk to more than 1 person at a time it may sound curt. Also I get up very early in the morning so I try to be prompt with my bedtime. Sometimes I get talking and have too much fun here and stay up too late and then I really have to hurry to get off - no long good byes.
The other thing that you mentioned that hit home with me was your friend's depression. Mine has flared lately and I'm really anti-social most of the time. I know that I've hurt friends here at PC, but right now it's hard for me to talk. I just want to loiter in the forums. IRL it's even worse. I have a hard time talking on the phone and I especially don't want to be around others. I'm just saying this because your friend may have had a hard time telling you. It may not be a deliberate attempt to avoid you, just a difficult time for her.
Give it some time and space and give her a chance to heal. I think others communicate the same on-line, but try asking your friends if they always get off-line so quickly or try talking to someone else?
Good luck to you. I hope you find some answers and feel better soon.
slow