This is an early test of the wills, and you can't afford to let her "win". The simplest solution is to STOP feeding her snacks to her. Let her learn to put them into her own mouth or do without the snack. She'll throw her tantrums for a while, but eventually she will start to feed herself. Keep offering good finger foods (cheerios, fruit snacks, crackers, etc.) but do not put them into her mouth for her. If they end up on the floor instead of in her tummy it's not the end of the world. She won't go hungry long. Her natural instincts will kick in and she will eat. Evidentally she already knows what it will take to make you do what she wants and she's challenging you.
Try a different approach. You could offer her snacks at a low table and allow her to come and go as she pleases while having them. I wouldn't do this for her meals, but this is a great way for her to learn that she has freedoms when she's feeding herself. Most adults don't sit in one place when snacking, so it won't hurt her to be able to roam a bit too.
There are lots of ways she's going to challenge your will vs. hers. Learn now how to recognize the challenges and face them from the start. Not only does this teach her independence,it also teaches her to respect you and her dad. Be ready for the tears though. They're coming, and they won't all be hers. It takes strength to be a mommy.
Good luck and God Bless!
L. C.
P.S.
A great website for encouragement for moms and dads is www.focusonthefamily.org with Dr. James Dobson. You'll find lots of great information on parenting there.