feeding baby solids after bowel resection

My daughter Cherry-Lee was born prem at 34 weeks with a twisted bowel. She had 60cm of bowel removed and recovered from surgery very quickly. Started her on breast milk very slowly. Cherry did her first poo in a week and all looked good. But the more breast milk we gave her the less weight she put on and her poo became watery actually frothy. We changed her to Alfare formula (predigested and lactose, soy free)and after 1 month she started to gain weight 20grams a day. We were disharged and cherry has been perfect health and weight gain since. Cherry-Lee is now 9months (7mnths ) and we started solids a month ago, first rice cereal farex mixed with alfare formula and after five days cherry became extremely gassy with dozens of burps and farts all at the same time and very uncomfortable.  I stopped feeding her the cereal and tried sweet potatoe with no bad reaction for 3 weeks and now i am trying banana no reaction after two days. i am extremely worried about feeding her. I am so unsure of how much her short gut may affect her in day to day life with food. It had been explained to me that when her digestion starts to work ( all the little cups fill up down the tract) it is then working properly. Will her bowel grow? Should i continue to worry about sort of foods i feed her? Just because Cherry had a reaction to farex should i worry about soy allegy? Are there conections to allegy with short gut? could there be problems with food in Cherry-lees future? Do you know of any similar cases i might be able to research?.  Thank you so much. Deb