Commercial sublease conundrum

[Eric Heyen]

My business partner and I currently have a tenant renting commercial space for her weight loss consulting business.  She recently informed us that she offers emotional eating and counseling type services with a certified addiction therapist.  Our tenant contracts the therapist, the clients pay our tenant and then she pays the therapist.  Our concern is that the therapist is also seeing her own clients at the space and paying our tenant for use of the space.  We currently don't allow sub leasing in our contract and have never arranged a sub lease, but we are not opposed to working out an arrangement so they can both utilize the facility.  Looking for suggestions on how to approach this situation.