I don’t understand why or how it is up to your daughter whether or not you pay for her insurance. Whether or not you are working has nothing to do with the basic issue, which is, who is driving the bus (in control of your finances), you or your daughter?
I can give you a way to fix this problem, but it won’t fix “the” problem. The problem is that you are letting her walk all over you for some reason, we know not why. What happens when you suggest she kick in a few dollars? Does she give you the guilt trip, about how things are starting to turn around for her and how your “selfishness” is going to mess everything up? If that is the case, you are being played like a fiddle, and I think you know that to some extent or you wouldn’t have posted. Perhaps you posted just to kind of get a second opinion that you are NOT selfish in making her pay. If so, you have it. You aren’t selfish. Quite the contrary: she is.
If you are getting the guilt trip when you get on the phone with her, avoid it for a bit. Write her a letter and don’t put emotion in it, just simply say that with loss of your income you cannot afford to continue paying her insurance. Include the phone number of the company and the policy number and tell her that she is free to contact them and get the policy put in her & husband’s name by X date, if not you are going to cancel it that day. Being factual and honest doesn’t mean you are being mean. And do it if it comes to forcing your hand. Cancel the policy and let her know it’s canceled.
You should prepare yourself for quite an onslaught of meanness, lamenting, and trying to put the guilt on you. Ignore it. If you really love her, make her grow up and take responsibility.