Can a non-exempt employee manage another non-exempt employee?

Yes, it is completely permissible for non-exempt employees to manage other non-exempt employees

In fact, employers are under no obligation to classify employees as exempt, even if they meet the criteria under the Fair Labor Standards Act. Employers may have an entire workforce of non-exempt employees if they wish. It is just very important to make sure that they are paid for any overtime and follow other wage and hour laws applicable to non-exempt employees.

Paysphere News | Federal FLSA Exemption Guide