I have been awarded PIP and have diabetes and depression. You should be aware that PIP is given based on how your life is affected, not what conditions you have. A well adjusted t1 with a good hba1c would get nothing. A person whose diabetic control is drastically damaged by their mental health should get something. However, from personal experience, if you are not seeing a mental health specialist, the dwp assessor will take one look and record 'doesn't appear mentally unwell', no benefit necessary.
The conditions the doctors put on getting the libre vary between authorities as far as I can tell. Mine says I would need to be bg testing more than the twice a day that I do. Like you, I find twice a day is as much as I can cope with. Why can't doctors understand that I don't want to stick pins in my fingers to make them bleed?
If you are going to claim PIP, the best advice I can give is get help to fill the form in (cab etc.)
About the depression, you are not alone, hang on there. Get as much help from your gp as you can.