My recollection is "none".
This is a study with an n of 1 that was expanded to an n of 2 and no controls or procedures in place to give one any confidence in the data collected. Maybe we could come up with a word for that, like anecdote but plural. Not data, maybe stories?
I wouldn't go that far (I agree that it's just an anecdote). She kept a rigorous food diary and also recorded her symptoms with similar attention to detail. She started by eliminating most foods from her diet with the intention of adding them back in one at a time (and thus hopefully finding the one or two things that might have been causing a reaction). That seems like a reasonable procedure for someone who has been sick her whole life and been put on many different drugs by various doctors, some of which helped more or less but none of which alleviated her chronic illness. There was no guarantee that diet was the problem, but it's worth trying, no?
The diet approach may not have worked, and it's entirely possible that her apparent recovery is just coincidental, but if it were me I'd continue with the one thing that improved my health.
None of that suggests that the diet that she happened upon is a good idea for anyone else. It's also worth noting that the long term effects may take time to arise, for instance in vitamin deficiencies, so she'd probably do well to try to track those things.
If she wants to recommend something to others I'd say it's the method of tracking foods/symptoms and noting correlations between them to try to eliminate foods that might be causing an adverse reaction. But I think that's pretty well understood by people already, and is too much work to sell to anyone.