Jett Reno is an engineer aboard the USS Discovery. Before Discovery she was an engineer on the USS Hiawatha during the Federation-Klingon War. She survived a crash during the war and spent ten months keeping her crewmates alive before they were rescued by the Discovery and became a part of their crew.
Reno is in charge of putting firewalls around the spore drive and propulsions systems of the ship to prevent the system from being infected by a power virus. She butts heads with one of the male engineers, Stamets, in the lab over the spore drive. He didn’t take her seriously as an engineer until they got trapped in the lab and had to work together to save a third starfleet member from being infected by a multidimensional fungal parasite. In the end they were unsuccessful and were infected by the spores, but they ended up being fine, and Stamets had a newfound respect for her. Reno gained the respect of the rest of the crew when she disobeyed Michael Burnam and helped fix and charge a crystal that would let them move forward in time.
At one point another member of Starfleet notices that Reno is wearing a wedding ring and she reveals that she had a wife but she died during the Klingon war. That is all that is mentioned of Reno’s sexuality but no one makes a big deal of it.