You are allowing this to happen. You need to decide on the menu... I'm not saying you can't give her choices, just don't let her decide the menu.
For example, you can ask her if she wants mac and cheese or a peanut butter sandwich.
When you sit down to eat dinner as a family, she should be expected to eat the same meal that every one else eats.
When my kids were little, the basic rule was that they didn't have to eat what I offered... but....
They got NO other food until the next meal. They didn't have the option of making a sandwich or bowl of cereal.
They didn't push that limit too often... and they are all very good eaters, and are willing to try new things readily.
I was not a short order cook...I cooked what my hubby would eat (which was just about anything), and they were expected to eat what we ate.
If you don't have the sweet things around, she will get used to doing without them.
And... don't worry... she won't starve herself! We forget how small their stomach really is.... a couple of tablespoons of an entree' is really enough... especially if there are veggies and other things there, too. Just don't get in the habit of letting her fill herself up on milk, either.