So, update, and it's good news all around.
She did have a heart attack. Yesterday, first thing in the morning, the cardiologist examined her and ran more tests, and they found a blockage in one of her main ventricles. We would later find out it was 99% obstructed.
They gave her an arterial catheter then, and put a stint in to open the blockage. Everything went well, and today she was discharged and could go home. She'll have to change her lifestyle, however, and she'll need to quit smoking (which will be the hardest part for her).
Thanks for the support from everyone. I stayed pretty calm during the whole ordeal, but certainly a part of that was being able to vent here while it happened.