@Camille she loves bananas but they don’t help and neither do the veggies we’ve tried. It’s really hard getting her to eat fruit other than bananas and apple slices.
I know they don't recommend fruit juice due to it being high in sugar but a small amount of fresh juice mixed with water may help if she would drink it?
My daughter was the same; we had to give her oat milk instead of cows and try and offer her more food, little and often. She’s a lot better now
I’m not an expert, but have you tried giving her fruits like bananas, steamed plantains or beans soup, mashed veggies soup? Fiber and fruits might help her