I feel like I have answered this question for you in about 5 different ways now, but here goes:
Yes, in my humble opinion it is too late for you to collect evidence through a PI on her behavior now. If you can find evidence in the past of her behavior prior to the date of separation, that would be helpful.
Most cases never go to court. Use the evidence you have in negotiations. Best of luck.
Janet L. Fritts
Attorney at Law
4101 Lake Boone Trail, Suite 500
Raleigh, North Carolina 27607
The response posted above is based upon the limited factual information made available and is not intended as a full and complete response to the question. The only reliable manner to obtain complete and adequate legal advice is to consult with an attorney, fully explain your situation, and allow the attorney sufficient opportunity to research the applicable law and facts required to render an accurate opinion. The basic information provided above is intended as a public service but a full discussion with an attorney should be undertaken before taking any action.