Jazz Jennings has been in the spotlight since 2007, when she was 6 and appeared on the ABC News program “20/20.” Wearing a dress, she opened up to Barbara Walters about being a transgender child, at a time when mainstream audiences didn’t often hear from those voices.

Thirteen years later, Ms. Jennings, now 19, continues to be an advocate for L.G.B.T. youth. She has had a doll modeled after her, written a children’s book and a memoir, and, with her family, started the TransKids Purple Rainbow Foundation. And she’s the star of the TLC reality show “I Am Jazz,” which returned for its sixth season this week.

TV viewers have followed many firsts in Ms. Jennings’s daily life, from going to prom to having a boyfriend. They tuned in when she had her gender confirmation surgery in New York City last season, surrounded by her parents and three older siblings. (There were complications after the surgery, and several follow-up procedures and visits with doctors were also chronicled on the show.)

Around the country, children and teenagers have watched Ms. Jennings go about her life at a time when some states are pushing back on transgender youth seeking the kinds of medical treatments the TV star and her friends have received. In South Dakota, young transgender people fear a bill that would restrict access to hormone treatments and surgeries on anyone under the age of 16. Similar bills have been introduced in other states including Colorado, Florida and South Carolina. (And despite the growing presence of transgender people in popular culture, the community faces elevated levels of homelessness, poverty and violence, especially for transgender women of color.)