Sensitive stomach too though Liz....bit of a minefield sadly. I did think of kitten food but wasn't sure knowing her stomach's the way it is.
Thank you. I'll make sure they're passed on - what a fighter of a girl she is. 
What is Dillen sensitive to, does she have a true allergy to a protein source (e.g. beef, fish, wheat gluten) or is it an intolerance, failing to digest carbs efficiently as many cats do? Have any tests or an elimination diet been undertaken? Often humans assume a sensitive tummy is because food is too 'rich' - to humans that means high in fat or animal protein as that is often what triggers us. Felines being obligate carnivores are evolved to eat 'rich' foods but of course any sudden change from a high carb to high protein (or
vice versa) may trigger digestive disturbance, as the body needs time to adjust the balance of digestive enzymes.
The easiest option is to go for a high animal protein/ grain free wet diet, because that cuts out most carbohydrates - which convert to damaging blood sugar - and limits the number of ingredients compared with dry. Butchers Classic (<50p for a large can) and Bozita (£1 for a large carton) have few ingredients which is useful in eliminating possible culprits BUT neither is a single protein source, so it wouldn't help distinguish between chicken or beef as the problem. HiLife chicken and Feline Fayre chicken (blue pack) are more expensive per kilo but both are stocked by Home Bargains at present (both 29p per pouch).
IIRC both are a sole protein source which could help with identifying the culprit but won't be suitable if Dillen is allergic to chicken! Again IIRC there is a little sugar in the FF and a little tapioca in the HL but both products will be substantially lower in carbs than the vast majority of dry foods.
Another option is to go all raw, again that eliminates the carbs and being sensitive to cooked beef does NOT mean you will be sensitive to raw beef because cooking denatures (changes the structure of) the protein allergen. The problem is the fosterer may not feel able to commit to it, the vet may not support it, the rescue may not want to put that burden on a prospective adopter AND of course Dillen may not take to it.
Can't honestly say that would be the route I'd choose unless eliminating carbs from the diet triggered a negative digestive response (allergy).
HTH.
