Some background info would help, like has she always been this way?, do u have children? if so were they born recently?
It does sound like shehas low self esteem, its kind of a case where if u think the worst of urself then u never have to fail cause u have already set the bar as low as it can go!
Have u tried talking to her about this? How does she react?
Many factors can cause these soet of problema/reations just a bit more background information would help.