I think my stepmom offered oral sex to a customer

My 41yr old stepmom who raised me since I was 5 owns a small beauty salon in town. She also provides massages. 90% of her customers are female. I was chilling at her salon last week because we were going to have dinner with some friends after she gets off work. A guy walked in and wanted an hour massage. I believe hes a regular customer because my stepmom seemed to know him. So they went into the massage room and I was just outside at the reception desk playing with my phone. About 45 minutes passed, my stepmom came out to the desk, grabbed her headband, went back into the room and locked the door. I did not realize anything was wrong until after 10 minutes I heard my stepmom moaning like "ummmm...umn...ummm", which lasted for about 5 seconds, then I heard coughing and spitting. She came out the room with her hair pony-tailed and used towels in her hand. She went straight to the bathroom and turned on the water, sounded like she was washing her mouth but im not sure.
Is it normal that massage therapists give bj to their clients? I don't want this to be true.