She's insectivore. There's no need to force her to eat fruits, so don't worry about her behaviour. Fruits, by the way, can bring forward dysbacteria due to high sugar content. There are some species eating flowers and plants from time to time, but Trioceros jacksonii isn't one of them. Enjoy your chameleon eating insects and don't worry if an insectivore animal won't eat frugivore food.