Hi and welcome to HCM.
It can last up to 7-10 days. If persist after this you should do ophtalmology and neurology work up.Till that she should rest i dark room,avoid physical activity and noise, eat easier food and drink.
It is unlikely that something serious could happen ,but you always should be caotious. If you notice sleeping disorder, vomiting
or tinhling in neck you should visit hospital as soon as you can.Wish you good health.