I will relieve your anxieties right now: this is perfectly normal! I have had 6 children and all of them (except the last one who is still a baby) have done this. I used to be anxious about it, but I did some research and found that all kids do this to some extent, some worse than others.
What is key is that her weight is not going down, she is happy, and not sick. If she seems to be fine, don't worry about her being picky about her food. What little she does eat in one day is actually enough for her right now. I think that must be part of the reason why kids take on so much fat when they are babies...when you can walk around and have such a good time, who wants to eat?
If you chart exactly what she eats, you might find a pattern over the course of a month or less. She might stock up and then not eat as much for a few days, and then maybe hardly anything. Then she'll eat a good amount for a few days, and just when you think it's getting better, she lays off the food again. She will be ok
Sometimes if you let her walk around outside or not buckle her in a chair while she is eating, she might eat more. My son was like that. He couldn't eat sitting down, but if I gave him a sandwich to walk around with, he would eat it. The same thing happened with my sister in law....her daughter was about the same age as yours and wouldn't eat. As soon as she let her out of the highchair, she started eating.
After a while they will want to sit a the table with the grownups and eat, so don't worry about forming bad habits.
I hope this helps. If not, feel free to hit me up with more questions!