picky eaters are trained to be that way. Nobody is going to like EVERYTHING that's put in front of them, but the kids who absolutely refuse to eat something refuse because they are allowed to (exceptions being those rare
children who actually have a medical/psychological reason for why they eat/don't eat certain foods).
The trick most parents miss is that you have to continue to offer foods to your children, even if they don't like it. Don't tell your child ridiculous things like, "Oh, you don't like X-foods, so we won't eat X-food anymore." Instead, tell your child, "Well, even if Y-food isn't your favorite, at least try to eat half of it, because Y-food is healthy for your body...." Um, that's provided that Y-food actually is a healthy food. If you're feeding your kid crap food that they refuse to eat, then it's probably healthier for your kid to go hungry that night!
The more you offer foods she doesn't like at first, the sooner she'll either start to like them, or she'll at least learn to tolerate them. I started all of mine out eating salads when they were 12-18 months old (just tomatoes and bell peppers at first, then lettuce and spinach later on). For the most part, they loved the tomatoes and hated the bell peppers at first. Over time, they've all learned to at least tolerate the bell peppers (one hates them, but will eat them first and "wash them down" with the tomatoes). They all hated spinach and lettuce at first, but then learned to eat it, and now all of them like it. My older two choose the big salad in the lunch line on occasion (NEVER on pizza day, though! They gotta draw the line somewhere)!
Too many parents underestimate their children. Children are extremely capable of understanding that food has vitamins and minerals that are beneficial to their bodies. They are very capable of understanding that certain foods are filled with artificial garbage that weakens and harms our bodies. Children are also extremely capable of manipulating their parents and using the things that their parents worry about against them!
If your daughter sees that you are completely stressing about what she is eating, then she is going to continue to be picky and she will use that against you. She is using her food choices to control you. Don't misunderstand! I'd be surprised if it was actually calculated on her part. I certainly doubt she's sitting up late at night plotting her next food battle with you or anything like that! BUT, when eating time comes along, you both fall into the same familiar habits (you stressing about what she eats, and her being picky about what she eats), and she knows the battle plan, because it's been the same from the beginning of her life.
Now you need to talk to her openly and frankly about her health, about her eating habits and about eating healthy verses eating garbage. Let her sit down with you at the computer and look at what eating garbage can do for a person's body.... then look at what good food choices can do. Let HER do the research (with you as her guide). Then let her know that you love her and because you love her, you'll be changing the menu and will be serving up a variety of healthy foods from now on. BUT, it's going to be left up to her if she eats or not. She can choose if she eats or not.
As far as snacks after a missed meal.... my rule is that if you skip a meal because you don't like what is served, you are skipping the next snack, too.
Don't cut out the garbage food cold turkey. Garbage foods have their place. The occasional garbage food meal won't (hopefully) kill you or cause you to gain a ton of weight all at once.... just don't make it a habit. We eat mac-n-cheese and chicken nuggets about once every two months or so. My kids think it's a great treat (frankly, so do I, because it's so dang easy!). We eat pizza probably once a week (even easier, which is why we do it so often!), but we also have a healthy salad with it, and we cut one piece of pizza in thirds and let them start out with 2 thirds, and then they can have the 3rd third if they're still hungry. Sometimes they do, sometimes they don't. All together, they only have one slice of pizza or less.
Be very careful about "diet" foods. Buy real food. Real butter, real mayo, real dressings, etc..... I firmly believe that man-made low fat foods are full of horrible artificial garbage that causes weight gain faster than anything else out there!
Introduce your daughter to the wonderful world of almonds. Almonds and raisins or craisins are a great snack. My daughters hate almonds plain, but they will eat them with craisins and raisins. I tell them it's good brain food, and good energy food.
If your daughter likes spinach, learn how to cook with it more. Have her help you plan and cook the meals. Let her experiment with different recipes. If she cooks it, she's more likely to want to eat it. Steer her towards healthy recipes, though!
Anyway.... I'm avoiding housework like the plague right now (it's a gift!). I hope something in this rambling can be of use to you!