Bewildered

She worked with us for more than six years.  She arrived on time, worked steadily all day, got along with everyone, and always behaved in a professional manner at the office.  She attended staff meetings as well as social events.  We all enjoyed  her easy smile and positive attitude.  Last week she called in sick for a few days then just stopped calling.  We heard nothing.  As suspicious as this was, some of us were still concerned something might be wrong.  I checked out Facebook and found no activity from her so I left a message on her wall, "Are you OK?"  She had a new profile pic and someone posted something about her new life.  The next day all of us who worked with her every day for six years were "unfriended".  I guess she's OK.  But what happened?  Why didn't she call and quit?  We may never know.  I'm bewildered.