Ah sweetie, the terrible 3's turned into the trying 4's. Maybe she bypassed the terrible 3's so you didn't have a heads up on how to handle her.
Number one, NEVER say, "then don't do it". First of all, she doesn't have a choice about a lot of things in life, and you can't let her think that she does. Secondly, she wants and needs you to hold the reins on her and be her boss. She wants and needs limits and expectations. If you get wishy-washy, inconsistent, and let her call the shots because you don't know how to parent her, she can't stand it and she will walk all over you with loud little boots that will crush your heart.
Believe me, she doesn't want to do this. But she can't help it because she doesn't know how NOT to do it. It is YOUR job to prevent her from doing it.
She will not be a happy, well behaved child if you don't rule the roost. If she doesn't want to sit down with you at dinner, tell her that she will have to go to her room and send her there. No coming out unless she is willing to sit at the table with you. No TV, no anything after dinner that is fun and usual. And more than anything, no eating anything other than what was on the table up until bedtime. She will be really hungry and mad, stomp her feet and scream at you. Ignore her other than to say, no more than twice, that she missed her dinner, but she can eat it if she wants it. And offer it to her no more than twice.
The next night she may try it even harder with you to see if she can break you down. Repeat the same thing again. Show no emotion to her when she is doing it. Send her to her room. Unless she is coming to that table to sit down nicely and eat, DO NOT allow her to come out of her room. Kids want your attention - they'll even take negative attenton, and they actually want you to argue with them so that they have a chance of wearing you down and getting their way (whatever their way is - as you can see in your daughter, she doesn't even know what she wants!). Don't fall for it. The only attention when she is fighting you at dinnertime is that she gets put in her room.
A few nights of this, being hungry, not getting anything to eat different than what she would have, and she will stop this stuff. Then you start working on the rest. When she says no to doing something, she either does it or she goes in her room and you take away a privilege in her schedule. When she ramps it up (and she will), send her to her room, take away a loved toy, AND take away a privilege in her schedule.
Throughout all of this, give her lots of positive reinforcement for all the good stuff. Lots of attention paid when she is behaving.
You'll get through this if you do what I'm suggesting - promise!