My t is female,older, about my mums age and I am 20yo female. I usually bring up sex really randomly within the session. Sometimes at the very beginning, depending on the past week. I feel comfortable talking to my t because I don't think she would bring up anything awkward and make me feel uncomfortable and let's me take the lead about how much I want to disclose.
I also like getting an adult/parental perspective, she has kids around the same age so she's fairly cluey. I have NEVER discused sex with my parents, as they were bought up with the no sex before marriage additude.