Diabetes & Mental Health Question

This is a stupid question and please pardon my ignorance on the subject. I have an older friend that is type 2 and uncontrolled/minimal controlled. They have had it for nearly 6-7 years now and I have watched them go from a pleasant optimistic person to a depressed cynic in that time, and covid crisis doesn’t help at all not that it needs to be said.

I asked them about the change in personality and got the worst response. They have “accepted diabetes will kill them and they have nothing more to look forward to.” They also “don’t want to be a burden” so they don’t want to meet anyone, make new friends, or date anyone. Getting them to go do anything is always an effort.

So back to my stupid question. Is diabetes and depression a thing? I think my friend should seek help, but when I say things I get responses like “If I was depressed I’d take care of it myself” or “I answer the questions on the doc’s mental health form and if they wanted to get access to that insurance money, they would send me to someone, the greedy bastards!” I think they are just masking because they have issues with trust and responsibility, but I don’t know any more since this isn’t the same person from 6-7 years ago. I’m not worried about them doing self-harm, but I miss my happy friend and don’t know how to help them.