Well, this sounds like a tough one because there could be a lot of different factors. I'm just going to throw out some ideas for ya:
#1 Maybe she tried something she didn't like and now doesn't trust anything that looks similar. My son hated almost all stage 3 baby foods, except for green beans with rice and sweet potatoes. So for the most part I just stuck with stage 2 and finger foods. I still give him veggies in stage 2 (even though he's almost 14 months old), especially during lunch, just to get something green down him. I think some babies have more distinct taste issues than others. And your baby may have a texture issue.
#2 I remember at that age, my son was feeling very independent and wanted to try to do everything himself, so maybe provide her with finger foods that she can eat herself. Try not to press the issue... maybe even walk away somewhere (if you're in the kitchen, do the dishes or something) where you can still keep an eye on her but not make her feel like you're intervening.
#3 Or another thing that I found is that my son would not (and still sometimes does not) eat unless he has some toys to play with while eating to distract him. I think sometimes eating is just another chore for him that takes him away from more fun things he could be doing.
#4 Could it be that her digestive system might be a little behind because of her premature birth? Maybe ask your doctor if that is a possibility. Also, if you want to give her yogurt, try Yo-Baby yogurt instead of adult yogurt. It's made from whole milk and uses a lot less sugar. It is, unfortunately, a little more pricey.
#5 My son can always tell when I'm tense and he gets very irritable (making me more tense/stressed). It's a catch-22. But perhaps your anxiety over her not eating is rubbing off on her and making it less fun for her to eat.
Whatever the case may be, maybe take a break from it for a few days and not press the issue. Then when she and you are both feeling more relaxed, try again using a different approach. Good luck!