Start by knowing that a child's stomach is about the size of their fist (everyones is comparable to this), so offer appropriate servings.
I am a daycare provider on a USDA sponsored food program and we have serving guidelines for healthy meals and portion sizes. Our instructions are to OFFER the foods. We can not force them to eat it. They will not starve. You need to stop this madness of forcing bites into her, or spoon feeding her to get it in (willing or not). At 3.5...thats nuts to me. I don't spoon feed past about 12-14 mos...EVER! Once kids are on table foods, they do it themselves. When we really start utensils I offer assistance, but they figure it out pretty quick thru trial and error and by watching me and older children (modeling)
Serving sizes are pretty small for a 3 year old. (USDA food guides)
Milk--1/2 cup
fruit/veggie--1/2 cup
Bread/grain--1/2 slice (or 1/2 cup cereal)
Meat/protein item--1.5 oz meat or 6 oz yogurt or 1 egg or 3 TBSP peanut butter
For the food program, we do breakfast (cereal or bread product, with fluid milk and fruit), Lunch (protein item, bread/grain, fluid milk and 2 fruits and/or veggies). If you do snacks they can simply be that small glass of milk with some fruit...or a few crackers...
I would go cold turkey on the treat type snacks. Don't even have them in the house for a while. She needs to be feeding herself and not be playing these food wars with you. No seconds on the things she likes. Pre plate her food...very small servings (the measurements are really quite small...get her a smaller cute plate if that might help it not look so overwhelming?). And just do not fight with her, cajole or bargain with her. When meal time is done, clear the plates, dump hers (or save it if you go that route..personally I don't agree with that). And NOTHING but an available glass of water in between till the next normal scheduled (by the clock or whatever) snack or meal time. And make it healthy. No cute granola bars or fruit chews or teddy grahams. Grapes and milk. Yogurt (not the kids kind..just get regular adult stuff...kids stuff has alot more sugar) and milk, a few simple crackers (cheese its maybe?) or saltines and a piece of cheese. Keep it small and simple so she will eat her dinner.
I manage this with children year in and year out (14 years now..and an almost 17 year old picky eater when she was small...daughter of my own). These kids all have their own likes and dislikes....and I try to work with that a bit....but I never serve chicken nuggets or fish sticks or that sort of thing. My daycare kids eat hearty spaghetti and baked simple tilapia (they call it big fish sticks..LOL)...and they feed themselves...even my current 10 and 11 mos olds...my 22 mos old and all of my 2 and 3 year old kids. No sippy cups either except for the infants.
Bite the bullet and just do it. I know some I offer similar advice to I also tell them it often helps to go shopping with the child and get a new "big kid" dinnerware set..start fresh...toss the "baby set"...even if its about the same thing...its a head game, but can help with many. Make a big deal out of it.
I wish you luck!