There is a connection between the immobility (of sorts) with flying and the air pressure changes that increase the risk of developing clots. An aneurysm is a ballooning of the vessel, and can happen to any artery, and because of the ballooning, the walls are weaker, risking rupture. If the surgery was successful, and the doc isn't concerned about her flying, I'd just suggest she get up every hour or so, and walk the length of the plane, just to get some movement of the blood.
Since my pulmonary emboli (several embolisms) in April, I've been told not to fly, or even ride in a car unless I can get up every 45 minutes to an hour and walk for 10-15 minutes. Pain in the butt, but better than the alternative. She could also get some compression stockings (ugly but useful) and wear those during the flight to keep blood from pooling in her legs- the bigger risk with flying than in her head).
The seizures around the time of her flying could have been coincidence, or if she had some infection starting (cold, bladder, etc), her period, etc. Even if she doesn't usually have seizures with those, flying could have been stressful enough (even if she didn't realize it- all of the checking in and out, security stuff, lines to wait in, etc) to push her over her seizure threshhold. Hard to tell. If the doc knows, and feels it's safe, maybe he could give her a bit of Ativan before flying, just to help calm the neurons a bit..... just an idea