2 year old doesn't listen

I feel like I'm in way over my head.

I have a 2 year old, and she literally never listens, shes constantly trying to find a new way to test my patience

Shes constantly yelling and screaming for no reason at all, it don't matter where shes to. She wont quiet down no matter what I say.

She always wants her way, when she doesn't get it she throws a huge fit, throwing things mostly, she'll run into her bedroom and slam the door as hard as she can, she'll push or hit sometimes lately too. And she screams bloody murder.

She won't eat, she literally refuses to eat anything except junk food, she loves cookies, I dont give them to her at all anymore, but now she just wont eat and fills up on juice, and waits for someone else to give her junk food, like one of her grandmothers. She sneaks it, like when I'm not around she'll ask someone for a cookie, or she'll manage to climb into the cupboard and take something junk related.

When I give her food, she throws it on the floor, or gives it to the dog. Even if she's hungry.

If someone leaves a pen or pencil or crayon out, the first thing she does is color on the walls

No matter what I do, she will not listen to me.

I dont know where this came from, she used to be such a good well behaved child.

Her father walked back into her life recently, about a month ago, and ever since then shes been this way, I dont know if shes learning this from his girlfriends daughter, or if shes just acting out, but I dont know what to do about it anymore