For general audit/internal control purposes, it is appropriate when reviewing employee accounts to review all accounts under the employee's control. This includes business accounts, non-profit accounts, and fiduciary (UTMA, POA, etc) roles.
As it relates specifically to employee overdrafts/nsf, your policy should consider what types of relationships/level of control are covered in the policy. Is this employee the prime driver/operator of the business, or just someone who is on the account for convenience purposes? Is the employee the primary originator of the transactions that are causing the overdraft? These are the types of factors you'll want to consider.
Finally, understand why you have an employee nsf policy in the first placed. One primary driver behind such policies is that they alert you to employees who are experiencing financial distress, and present an increased risk to the bank of possible misappropriation or coercion. An employee who is try to keep a struggling business propped up (across 14 accounts), IMO, presents a greater risk than an employee who is having a hard time managing a personal account.