MIAMI — Kaitlyn Hunt’s parents insist that their daughter, a Central Florida high school senior, is being prosecuted for sex crimes only because her lover was another girl. The state attorney says that gender makes no difference; the age of the two girls is at the crux of the case.

Ms. Hunt, 18, is an adult. The girl with whom she allegedly had sexual encounters is 14.

Ms. Hunt, described by her parents as a happy, hardworking girl who played on the basketball team, sang in the school choir, helped mentor other cheerleaders and taught gymnastics to younger children, became an international cause célèbre over the weekend after details of her arrest and pending prosecution exploded across the Internet.

Between Friday night and Tuesday morning, more than 100,000 supporters from around the world signed an online petition siding with Ms. Hunt’s parents. About 30,000 supporters, some from as far away as Australia, South Korea and the Netherlands, had joined the Facebook group Free Kate.

The police arrested Ms. Hunt on Feb. 16 at her mother’s home in Sebastian, near Vero Beach, charging her with two counts of lewd or lascivious battery, a second-degree felony. According to the arrest affidavit, the two girls, who knew each other from the basketball team, began a relationship in November. Just before Christmas, they had a sexual encounter in a bathroom at Sebastian River High School. They had at least one more encounter there, according to the affidavit, and one in Ms. Hunt’s bedroom in January after the 14-year-old, a freshman, ran away from home.