PIP

You have to prove that she is unable (not unwilling) to living independently.

I can't see how diabetes on its own will ever be enough for someine to qualify for even the lowest rate.

Hi there, I am guessing there is more to the care of your daughter than diabetes? x

If she qualified for DLA then fill in the PIP forms with the same information. If her health status hasn't changed.

In my experience forms are just as long. DLA covers hearing, sight, sleep, mobility and how their medical condition affects getting from A-B and daily activities.
PIP covers medication, mobility. Cleaning yourself with or without help. Planning a journey. How your medical condition affects your daily activities. PIP forms allow for extra info from specialists and medical treatments and how medications affect you.

Type1 and insulin can affect young people and their socialising (like their peers) dramatically. All worth mentioning.
Inconvenient hypos or anxiety to learn to drive etc....
Forgetting insulin and any A&E visits all should be mentioned too.
Financial costs due to disability does have a bearing.