Notify your homeowners insurance immediately. They will handle it. The issue is whether there was something about the property that was dangerous or you were somehow negligent and that caused her to crash. If she suffered a head injury and if there is a bike helmet law in your city/state, then she may have some responsibility for some of the injuries in any event. If you are not insured, you need to contact an atty immediately to be sure they dont get a default judgment against you.
As stated, turn it over to your insurance carrier, and do so ASAP. Delay may affect coverage, as you have a duty to cooperate with the insurer. HO insurance is a wonderful thing, and I have seen it come to the rescue of many a family facing a claim of some sort.
This comment is general in nature and is not intended as legal advice. It does not create an attorney client relationship and obviously is not confidential. You should contact an attorney in your area who can review with you all of the relevant facts and give you specific legal advice.
Sign up to receive a 3-part series of useful information and advice about personal injury law.