My husbands ex as since married twice. Who’s social security can she draw on? No 3 was only 4 yrs. No I was 20 yrs, No. 2 16yrs
Your husband's ex could potentially draw benefits on any ex-spouse's record that she was married to for at least 10 years, or for as little as 9 months if the marriage ended in death rather than divorce. She could only draw benefits on one ex's record at a time, though, and only if she meets all of the other entitlement requirements (https://www.ssa.gov/OP_Home/handbook/handbook.03/handbook-0311.html).
By the way, if your husband's ex does draw benefits on his record it would not adversely affect either your or your husband's benefits.