Welcome to HCM.
The headache must be due to post surgical stress
and very common in such age groups. Take her back to your eye surgeon for a review and make sure he assures your mother directly that everything went fine with her surgery. Let her talk to her doctor.Once she is relaxed and relieved about her queries ,then she will be fine.
You can request him for the medicines for emergency use.
Please take any medication under your ophthalmologist's guidance. Hope your mother gets a good sleep. Take care.