Unfortunately, you can't buy extended health insurance just for your wife. However, there are some other options that are available. It sounds like your best bet would be to purchase COBRA through your, soon to be former employer. Policies are effective up to 18 months and you will need to pay the full premium every month. Just remember that you will need to elect to purchase COBRA within 60 days of ending employment. Fortunately, the process to do so is rather straightforward and you should receive instructions in the mail on how elect COBRA. Your other option would be to try to purchase individual insurance for your wife. Due to the fact that she has diabetes, you may run into quite a few obstacles trying to find a policy to cover your wife. Even if you do find a policy to cover her, you might discover that it's very expensive. It's a good idea to seek the assistance of a licensed insurance agent to help you find an individual policy that would cover your wife even though she has diabetes.
Many individuals put off retirement and continue working a few more years until their spouse is old enough to qualify for Medicare just so they can provide health insurance for them. If you would still like to retire, but can't afford to spend a lot on insurance for your wife, she may want to consider finding a parttime job that offers health benefits. There are some employers that offer health insurance for their employees and may even pay part of the premiums. No matter what you decide to do, just make sure that you don't have a lapse of coverage. With your wife's preexisting condition, it could have huge financial consequences if she needs medical care, but she doesn't have insurance.