Any kind of conflict can be made into a food fight. You're in the right in this case - fruit is better for you than sugary snacks. If you stand firm about this, eventually she will probably join your dieting efforts. Or not. Sugary snacks are everywhere - outside the home, so it's not as if she's always in a sugar desert!
Ah, for the good old days, when a kid could complain about mom in a diary, not on facebook...