Throughout the movie it is referred to as a she.
It's been long since canonized that Turk is female
Terk, short for Terkina, is a character from the 1999 Disney animated feature Tarzan...In the original book series, Terk was a male (and his name was short for "Terkoz"), and he was not a sympathetic character. Originally, Terk was going to be a male like in the books, but the reason this was changed was because when male actors auditioned for the role, none of them worked, when Rosie O'Donnel auditioned, it worked out and she got the role. Some audiences of the film mistakened Terk for a male.-- Disney wiki
She's referred to as a 'she' in the movie, and most people only think she's male because she looks androgynous and she has a lower voice.
in the beginning of the movie, terks mother referrers to her as a," young lady ."
turk is a boy