Certified Audit

I had an ex who rented my condo and we ran into some issues. I sent the check by certified mail and it does not pick it up, I think she tries to move past the deadline for the return to cause problems. Should I contact her to proove I notified or simply wait until the letter is returned to me?

Whether it be returned. DO NOT OPEN and keep it. It is legal proof of service, she did not pick it up. The judge in the open and any writing is required, it will not matter that she refused.