Mom and the Thunderclap Headache

Last Sunday my mom, T and the three guys from Holland took the train up to SF for a day of touring, cable car riding and general exploring.
At one point we were walking down Powell and saw an elevator on the outside of the Fairmont Hotel. It looked like a fantastic vantage point to check out SF from high up. But to get to the entrance of the hotel we had to hike up Sacramento Street. From Powell looking up, it appeared to be at a 45 degree angle. Yikes. But only one city block, so we crossed the street and started the climb. We were all huffing and puffing in no time, and all conversation ceased without the breath to speak. Near the top of the hill, mom started to moan and said there was a knife inside her skull to the right side. It stabbed her with every heart beat. We were all pretty worried but she seemed to be recovering quickly, once we had her sit down, catch her breath and drink some water. And then a woman from the hotel staff walked by and said she used to get bad headaches when she wasn't used to walking the hills too. So we all felt a little better with that bit of information.
An hour or so later we at Lombard Street. She had been waiting there as she arrived in a cable car ahead of me. We decided to walk down the crookedest street and then take a picture from the bottom. No trouble here. Nice views too.
But when we were walking up the steps, Mom suddenly fell. This is always scary since she's been diagnosed with osteoporosis and has broken both elbows with falls in the past. She said her "leg just gave out" and she hadn't tripped. Thank goodness she didn't break a bone but her wrist was sort of sore.
The rest of the day she seemed absolutely fine. We did a LOT of walking and normally she's behind me in speed but this time I was the slow poke. I'd forgotten all about the horrible headache she'd had.
The next day, she said she was sort of sore all over, her arthritis was bothering her and that headache was still with her. It wasn't anything like it was but still sort of nagging and making her tired. But she blew it off and took Motrin.
Now it's Wednesday and the headache is still there, and now that she is looking back she also had some nausea on Sunday night and it's kind of back again.
Now I'm getting really worried. Maybe I should have been worried right away.
Of course, googling "sudden headache with exercise" brings me to some scary potential diagnoses: Subarachnoid bleed. I'd thought of stroke in the first moments but those usually don't hurt and there was no weakness or facial changes. Oh, heck. What do I really know about stroke or brain bleeds?? I'm in REI! Not helpful.
So today I insisted that she needed to call her doctor. Thank goodness he's on the ball. He ordered a CT scan and she's there right now. And freaking out a little too.
God, I hope we're just fearing the worst and she'll be fine by tomorrow.