I agree with Tammy.
You're doing the right things.. but maybe offer her some "choices" at mealtimes. Not different from the rest of the family perhaps, but several items, not just one dish (pizza; mac n cheese; PB & J). I NEVER give my kids ONE thing.. They always get 3. Sometimes more. They must eat a good portion of the main dish, and one side and a taste of the other.. they can usually choose which. But they are older and past the issues you are dealing with. Offer her several SMALL servings of something.. (If you are having cut up squash, put 2 bite sized pieces on her plate, and expect her to want NONE of it, but encourage her to try one bite only, she has to option to leave the other one).. THen the next time... maybe just let it sit on her plate... if she wants to have it great. If not... well.. she'll find SOMETHING on her plate to eat... right?
I found with my picky eater, that simply too much food on the plate is overwhelming. So make it simple and small.. If she wants more, you can always serve more after she requests it.
Don't let her snack but once per day (keep it healthy and SMALL and YOU control the schedule she receives it on.. don't let it become a substitute for her meals i.e, don't let her have the snack within 2 hours of a meal - usually 3 pm is a good time if she is up from any nap). She will eventually eat.. but if you give in and make her what she wants, she will just learn that if she waits you out, that you will give in... just like any other power struggle. If she has not eaten a large variety of foods already, then she may really not like them.. but only actually eating foods that have a variety of flavors/textures will help her LEARN to appreciate them.
My kids like plain foods (olives, cheese, cucumber, raw carrots, iceberg and romaine lettuces, berries of all sorts - blackberries, raspberries, strawberries, blueberries- grapes, bananas, steak, grilled chicken (no elaborate marinades).. etc. Even cereal dry, with no milk.. and not the sweet ones. Mine like cheerios, special K and frosted mini-wheats. Some kids don't like any kind of sauce (my daughter) AT ALL.. even BBQ on ribs, or melted cheese; some kids like to dip everything in something (ranch dressing or catsup). So try to figure out which way she leans. Offer her a small cup (I use those 3 oz bathroom cups sometimes) with a little dressing or catsup in it to dip in. You can even put yogurt in it to dip things in. If she wants, she can dip; or not.
Sit down for a meal. When she has eaten 3 bites (if you want to do use this option) from her plate she may be excused. Otherwise, she will sit until the meal is over.. then she can take her plate to the kitchen (where you will wrap it with saran wrap and refrigerate). Then she can go do whatever... when she is hungry (15 minutes later...) she gets the plate back.
I would think she will learn to eat a few things pretty quickly... it will be harder on you than her. But hang in there. And enlist the aid of your family.. they cannot undermine you by giving her snacks (or special food) or it won't work.
I hope this helps.