I agree with the above tips. Right now, solids is more for getting used to tastes, textures, as well as the concept of eating food. Also it's not uncommon for kids to go through stages of only wanting one thing to eat, at any age range.
Like pp have stated, your DD doesn't need anything but formula or breastmilk until the first year. With that said, the only way my DD would eat solids was if I chopped/diced/smashed it and she could feed herself. She absolutely REFUSED to eat any and all baby foods because she couldn't feed herself. DD is now 13 months old and is still like that. Lol. Just keep introducing foods, Mama. It'll take a few times before she accepts it.
She actually does not need anything but formula at her age. If all she wants is bananas, and it is not causing her problems, let her have them. I mean, I wouldn't give them to her 3 meals a day or anything, but I wouldn't force other things on her either.
Dont worry,. My doc always said baby food was for practice really. He also told me at this age as long as she is eating she is fine. Later on when you give soft mushed table foods she can get more practice with other flavors. My First DD would only eat squash carrots and sweet potatoes. LOL Now she wont touch them..