Do you know anything about Cocco's history before you got her? One of my gliders that was a rescue and had been in at least 3 homes before joining my family was a biter also. She looked like she had been teased with treats. When I showed her a treat she would grab at it with both paws and try to grab it with her teeth all at once - frequently missing and chomping on my finger in the process. I used a small baby spoon to hand her treats until she learned that if I offered it to her it was hers to eat. No teasing here.
It took a couple months before she trusted me enough to take a treat gently from my fingers.
Be very patient with Cocco. Try offering licky treats on a straw or a spoon handle. Even a popsicle stick would work until she learns to trust you enough to stop biting.