Legal Question in Personal Injury in California

That is a difficult question to answer. One would not anticipate parking a car across the street would be bringing it within a zone of danger of being hit by a rock. Likewise, the gardener wold not anticipate that his work could result in such damage occurring, so there may be no negligence and thus no liability [not all accidents are compensable]. Also, it was the gardener who is an independent contractor who may have caused the accident and his fault, if any, may not be attributable to your mother. That apparently is the position of her insurance company.

The standard insurance contract imposes on the insurer two duties. One is to pay for all damages, less deductibles, caused by the negligence of its insureds, and they might not have any duty under that provision. But the second duty is to defend you against any lawsuit alleging that you have a duty to pay the other side. So her insurance carrier must pay for an attorney to defend her against the suit; if they show she has no liability and thus they have no obligation to pay for the damages, they still must foot all the bills for showing that. If the other person has insurance, it would be cheaper for the insurance companies [your mother's, he gardener's, other person's ]to refer the matter to inter-company arbitration to decide who should pay what. Ty to get them to waive the deductible as there is a conflict between their having to defend your mother and wanting to spend the least amount of money so they might not defend her very well.