My oldest child (6) has been like this since he was 3, so I completely feel your pain. As long as her doctor says she is healthy, I wouldn't be overly concerned.
Like some of the other moms have siad, try not to keep junk food in your house, or at least, keep it where she cannot get it. I keep junk food over the stove cabinet and the kids know that is there, and they also know that they will be in huge trouble if they climb up on the stove to get it, so they forget about it most of the time. Also granola bars, gummys, grapes, nuts and bite sized veggies make great snacks and are healthy too. Both of my children love raw veggies such as carrots, celery and broccoli and are content to snack on them when they have the munchies.
As for meal times, I am not a short order cook either. The kids have what the adults have for dinner and they either eat it, or they're out of luck. One trick to that (and it sounds horribly mean but I guarntee that you won't have to do this more than once or twice) is to put the plate in front of her and let her know that is what she is to eat. If she doesn't eat it for dinner, you will warm it up for a snack, if she doesn't eat it then, you'll warm it up for breakfast, if not for breakfast, then she can have it for lunch (etc, etc)
I wish you all the luck, picky eaters can try anyones patience!