Emma I would not think that it is an allergy per se, or even an 'issue' with fructose - just a case of too much fruit. Fibre-wise, babies need
Babies/toddlers still need (in Engald) 5-a-day but what counts as one serving is much less than an adult. For babies and toddlers it is what will fit in the palm of their hand. So about 1/4 of a banana, a small piece of pineapple, a few chunks of mango, a quarter of an apple. So if D is having a full banana that is a good portion of her daily fruit and veg requirements there.
Fibre-wise, babies need their age in years plus 5g to 10g to make up how much fibre they need. So for D that is 6-11g of fibre per day. One banana is 3g, 1g in a handful of raisins, half of a pear is 2.5..then her breads and such, and it could just be a fibre overload. That and more than the needed amount of vitamin C typically causes cramps and bloating and diarrhea. So that also might be a factor - I know even now my DS can only eat half of a kiwi in one day, the combinatio of fibre and vit C in it is too much and he gets pretty soft poops.
The other thing to keep in mind is that the bowel absorbs sugar in order to work - and needs to. But too much sugar (so fructose) and it will definitely cause some digestive issues. But it doesn't mean she is intolerant/allergic, etc ... just that she is getting too much for her own system, kwim?