Yes, your sister definitely needs help. No, this does not sound like attention-seeking. Take her to a psychiatrist. I cry all the time too and it's so embarrassing. I never know when a thought, a memory, or something someone says will trigger it, and off I go again, crying and crying. For no good reason. ...I am a teacher and I have major depression. I take medicines, have talk therapy with a counselor, and soon my psychiatrist will have me in outpatient day classes again. I take it a day at a time, and some days are better than others, fighting that dark cloud within.The best thing you can do is be there for your sister, offer her support, and insist that she go to a doctor--and have someone else in the room with her and the doctor. You all need to know just what she's going through.