X is trying to get separation agreement set aside

My spouse signed a separation and property settlement agreement 10 months ago. We agreed on it together. I took it to my attorney who wrote it up.
Attorney explained that I was the only one represented by counsel and a seperate form was signed to that effect. She opted for lump sum upfront so she could move out of state, which she did right away and payments over 5 years when the house sells. I took all debt etc. Now after 10 months she hired an attorney and they are threatening to sue to get the agreement set aside unless I renegotiate all the terms. How likely is it that this agreement can be set aside?
Does this happen often?

The agreement will not be set aside unless your ex can show that she was incompetent at the time the agreement was signed, or that she was coerced or under duress when signing the same.