M.F.
This question gets asked all the time on this site, and it's one of my faves to answer :-). First, thing is some advice a wise mom gave me when I had the same concern: "You will never win a battle over food." Second, is that she'll eat when she's hungry. And, at this age, her choice isn't so much about what she eats, but whether she will or not. You get to choose what's offered. Granted, if there's something that my kids really, really don't like (take peas, for example), I'm not going to force it. But I'll bet she's not "picky" -- she's just not terribly hungry most of the time. Kids' growth slows down a lot between 1 and 2 yrs old, and doesn't really pick up again until they're nearly 4.
Kiddos her age really don't eat much at all. It's hard for us as parents to see them eat 3 tablespoons of yogurt, then leave the table. We want the yogurt cup empty so we feel better about the meal. Will she be hungry 2 or 3 hours later? Probably, but that's the nature of a toddler. They need to replenish their energy often!
You're wise to be concerned about this now, because you're laying the groundwork for future eating habits and nutrition.
I'd recommend that you offer a balanced meal for her, then don't say another word. If she says something is yucky, say "That's ok" and try not to make anything an issue. Distract her with songs or ask what her favorite color it, etc.
If she throws a fit at the table, plays, etc., she's probably not hungry. A hungry kid will eat. Period. (Remember when she was a baby, desperate for a bottle, and you couldn't seem to make it fast enough?)
One thing we say often at meal time: "You may eat nicely at the table, or play on the floor (or in your room, etc.)"
or "Eat what you need to have enough energy until the next meal." This way, if they're not hungry, they have an option. As the kids got older, we've enforced keeping them at the table for family time by asking questions, playing games like "I Spy" etc. At 18 months, it was simply easier to let them play while we enjoyed meals in peace!
Also, I'd heard that kids need to see a new thing about 14 times before they'll try it. I decided to try this experiment. For my daughter, it was steamed broccoli. I kept it in stock and offered a tiny bit every day for dinner (without saying a word about it), and even for lunch if I thought of it. About 12 or 13 days later, she ate it. With my son it was blueberries. I put two blueberries on his plate at breakfast. On day 15 he ate them, and now loves to top his cereal or yogurt with them.
Also, my favorite story is from when we really decided to crack down on meal times and nutrition. We simply offered a balanced meal and sat down at the table (and we usually make sure at least one thing offered is something we know they like). The kids were 1 and 3. The main problem was with my daughter. My son has always eaten everything we put in front of him :-). If there was fussing, etc., we sent my daughter away to her room (You may join us for a family meal, or wait in your room until we're done). She's pretty strong willed, and held out a while -- she may have missed most of 3 or 4 meals. (note that she didn't starve -- food and drinks were always offered, and she typically would eat a little something at breakfast). When I thought for sure she'd have to give in, I made salmon with rice and asparagus for dinner. She ate every bite! And didn't say a WORD.
Another thing we learned is that kiddos can tend to drink all of their calories. If she's having a glass of milk before meals, she'll feel too full to eat, and have plenty of energy to exert her will about what she'll eat, or whether she'll sit still at the table. At her age, she probably only needs about 12-16 ounces of milk a day. We started offering water at meals and noticed both kids eating better.
I hope all this helps, and good luck feeding your little one :-)