Good afternoon Kathleen,
I'm Doug, and I'm very sorry to hear of your situation. My goal is to provide you with excellent service today.
If the homeowners insurance is only in her name, yes she can cancel it. If it is in both of your names, then call the carrier and tell them not to cancel the policy.
Under CA law, generally the person living in the home pays for their share of the expenses and in your case, 45% of the fair market rent to the other owner---but each owner pays for their share of homeowners insurance, taxes and maintenance expenses as well as her share of the association dues.
However, as co-owners you are free to agree to any kind of a shared expense agreement that you want to choose. But if you cannot decide, then either of you can sue the other and force the sale of the property, or force one owner to buy the other out.
You may reply back to me using the Reply link and I will be happy to continue to assist you until I am able to address your concerns, to your satisfaction.
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I wish you and yours the best in 2015,