Justin Bieber harassed a woman at a North Carolina gym Tuesday and maybe even spit in her water bottle -- at least that's what she says. Justin's camp says she's lying.

Colette Harrington, a North Carolina radio host, claims she asked the Bieb for a picture, but he said no. When she returned to working out, she says, she heard Justin and his posse mocking her. Colette explains, "I always count out loud my reps. Then Justin starts imitating me and whenever I'd get to 20 he and his buddy would say 'Shut the [F---] up.'" Then, she claims, someone -- possibly Justin -- spit blue Gatorade into her water bottle while she wasn't looking, and she later drank it.

Colette says she's going to sell the spit-filled water bottle on eBay and plans to use the money to upgrade the kitchen at her local Ronald McDonald house, where she volunteers.

Bieber's rep tells TMZ that Justin and his trainer were in the gym, and they were making snide comments to each other, not to the Colette.