Hi there and thanks for your question Luanna.
If a kitten is 6 hours old (I'm not sure if this is a type on your part?) they need to feed every 2-3 hours, ideally from mum.
If mum cannot feed, we would have to bottle feed.
If you mean a 6 year old, they can graze feed (as long as a healthy weight) or we would have a couple of set feeding times each day. (I assume it is you that is the diabetic rather than the cat, as advice would be different for a diabetic cat).
With regards her biting/scratching, this sounds like petting induced aggression.
The issue that you are experiencing is actually not as uncommon as you may think and is a reason that many owners will seek assistance. This is particularly true of cats that are rescues or were feral or semi-feral as they often did not receive adequate socialisation and integration with humans when they were in their key developmental stages in their first couple of months of life. While the best time for them to learn to socialise correctly with humans is when they are kittens, this does not mean that they are beyond help and there are certainly things what can be done.
Petting induced aggression occurs when cats are feeling very comfortable, are perhaps purring and enjoying a head scratch. They are really relaxed and suddenly, for no apparent reason, they put their guard up and may hiss, bite, scratch or run away. The theory is that they have suddenly realised that they have let their guard down and feel vulnerable so quickly act offensively in fear of something bad happening. It's sad really, that they can not just enjoy being content but feel that something bad may happen.
Our aim is to minimise and eventually eliminate these events.
Be sure you are reading her body language. At the first sense of a bite coming on, remove yourself from the situation. Watch for ears down, freezing, tail wagging etc. Some cats give lots of clues, while others do not.
Ideally, you would see a pattern to her behaviour e.g. she will tolerate petting for 2 minutes and then becomes impatient. Try to pre-empt him and stop a petting/cuddle session after 1 minute. If she has been really good the whole time, reward her with vocal praise and a treat. Of course, if the session ends badly, she gets no praise or treat.
It is useful to build her confidence and sense of security so she feels less inclined to lash out. This is done by enriching his environment with interactive toys such as laser pointers and battery operated mice, as well as food puzzles, cat mazes and cat tress. Some cats also enjoy catnip toys. Be cautious to not use your hand to play at any time, as this can increasing hand biting tendencies.
Another consideration would be stress-reducing products such as calming supplements in her food each day (e.g. nutracalm or Yucalm) as well as a Feliway plug-in.
A final consideration would be to have a vet check if she has not had one recently. This would just be a nose to tail check to ensure we are not missing a source of discomfort or discontent such as a bad back tooth or any joint pain.