She's obviously on medication and some of the T2 drugs can produce hypos. (note the mention of glucose tablets in the article) Not eating regularly is going to increase the risk of severe hypos.
http://www.diabetes.co.uk/severe-hypoglycemia.html
It is well known that hypos reduce the ability to process information because the brain is being starved of fuel. I remember being told one way of checking to see if I was going low was to try some multiplication in my head! I know when I do have hypos that I want to get away from people, talking at me and retreat into myself I would think that a TV interview when hypo would be a nightmare situation.
I'd be the first person to say that diabetes shouldn't stop you from attempting to do anything but it's also important to realise that it is only possible to do anything when the condition is well controlled. There are times when other events or simply trying to do too much can get in the way of that. That's where she, or Theresa May or any of us really needs someone near us who is aware of the potential problems (and our symptoms)
Pragmatically, Diane Abbott, increased her majority, I presume that the local populace consider that she has demonstrated her abilities as their MP.
The important message to get out is the symptoms and treatment of a hypo.