EDIT
So we have to assume if for example you drink a glass of fruit juice the fructose spike in your blood stream will peak in about 15 to 20 min and start nearly instantly because Fructose and glucose are also adsorbed through the skin of the mouth and throat.
Fructose and Glucose both act like a salt and have a high osmotic pressure. I'm assuming this otherwise it would not go through the skin of the mouth so very quickly.
Therefore it will permeate all organs within a few seconds to max 20 min.
The breakdown of the Fructose will take a certain time depending on dosage and your ability to dump Fructose. This both is genetically influenced and also dependent on how close you are to becoming a diabetic.
We have to assume Fructose will cause diabetes in everyone (or at least 85%) if dosage is high enough.
My cousin worked on Seismic servery through out Africa for many years, (looking for Oil).
The crew were given Coke for free as liquid to drink (you have to drink a lot in 45+ degrees C and even more if you are doing a hard physical job.
He drank water which he bought because he did not like sweating Coke like sugar solution!
85% of the people who worked for the company in Africa are now diabetic and are suing Coke a Cola for damages.
OK back to spinach I can only manage a little spinach and even then I have to remove the stalks and the main "veins" on the leaves, I do this with a sharp knife and cut them out. I then can eat it. I eat both summer and winter spinach (the summer version is just young leaves the winter version is more like green cabbage leaves)
I find in green plants most of the sugar is kept in the white pithy stalks (if the plant has no significant underground root to store it in like a turnip or Rhubarb)
If a plant has a large root to store the energy in, for example rhubarb or beetroot then the stalks contain very much less sugar in them, and are usually HFI safe ('r).
I use young beetroot leaves in a salad to give it lots more colour and make it look better, if I'm preparing food for other people to eat as well as myself.
I do not go mad cutting all the veins out but do not myself eat too many of the stalks.
The green tops of the leaves on spring onions (scallions) are safe'sh although they tend to give me wind and digestive problems if I eat too many too often.
None of these would I recommend in the case of Nicoleh's daughter because she is very sensitive indeed.