I stumbled across this thread while asking the same questions as many here. Like much poetry it evokes but doesn't explain.

The portrait it paints of this woman is compelling and, as far as it goes, familiar; a woman hollowed out by loneliness to the point that she can't even weep for herself (I think that's a second meaning for the title; we have to weep for her because she can't any more).

As to her past, there are scattered hint but they are all highly ambiguous and I don't think its possible to come up with a definitive picture of what has come before.

"She lives in the land where her father died. "
"And the fourth deepest wound and the love that it killed."

These are hints that are are open to countless interpretations. Sexual abuse? Maybe. An abortion? Maybe. A traumatic love affair long ago?

Another thing to remember is that, given the artists and the period, there may be a lurking anti-war message; perhaps her father died in 'Nam and she never got over it. Yeah, that's pretty speculative but makes as much sense as the other explanations.

We're not meant to know.