I don't believe "sinus infections" are a common cause of siezures. That's absurd.
On the other hand everyone can have a siezure induced under the right circumstances.
Flickering lights, especially red lights (such as on a police car) or strobes are the most common causes of siezures. Pilots of fixed wing propeller aircraft and helicopter pilots have developed siezures from the flicker of sunlight through the propeller blades.
Singlasses are sometimes prescribed for those susceptible to "light-flicker" induced siezures.
The diet sugar substitute aspartame has been linked to siezures.
Usually anti-siezure medication is not prescribed until the second or third siezure.
Meanwhile, it's a period of "watchful waiting". Be especially awar or what are called "petit mal" siezures, which are momentary lapses of awareness and consciousness, often with the patient staring into space, unaware of his/her surroundings. Sometimes an MRI or electroenchephalagraph will detect a brain abnormality. Often as not they will show nothing.
Usually a siezure is preceded by what is called an "aura", sometimes a metallic taste on the tongue. If driving, this means she must pull over immediately.
I wouldn't be overly concerned over a single siezure, but the patient should not hesitate to see a physician immediately if it happens again.