Keep quiet. DO not contact her. Let her go on beliveing that she has time. SHe does not. If she does not see a doctor, she cannot make a medical claim in any way, shape of form. The fact that she already claimed to have neck pain is not a good sign for you. But you may argue that must have been a "pre-existing" condition b/c whiplash takes time to show symptoms - period. The time limit for seeking property damage in AB is 24 months! Yeah that shocked me too. But at least in court common sense does preside. Most judges won't even hear a case unless a "reasonable" timeline for claim is followed up w/ proper documentation.
BTW, the headrest defence only in AB if your Ins. Co. investigates it. See, in AB the province has made very public efforts to make drivers aware of the dangers of poor headrest position. I've seen many cases thrown out b/c the injured person had "no reaon not to know better". That the AB way.