Firstly don't beat yourself up for her "pickiness"...it, just a host of other things to come, are phases. As long as you haven't attributed her behavior or food choice decline to anything regarding a health issue, then she is probably being just that - picky.
Giving her choices will help her to know that there are so many things to choose from and that she's not always going to get her way. Sometimes you may offer her a choice of two things that she doesn't care for...but let her know that at next meal time or snack time she can have "x" (something she likes).
Be careful of giving in to only the things she's "into" because then you'll have an ever harder time of getting her to grow the variety in her diet.
My son is now 3 yrs-old and he's had some of those picky times when he doesn't want to eat what I have given him. I really thought he'd never eat table food or anything besides snack foods - but I continued to offer him a variety as well as told him that this is what there is to eat. So he could eat it & then get a treat or not.
Although I'm not so into making deals, we sometimes have to use what we can to get the children to do what we know is best for them.
It may take time...but she should come out of this. Also ask your pediatrician if she's lacking any particular nutrients and if she may need some supplementing from other vitamins, minerals, etc.
I wish you the best!