I'm 42 years old. I've been very active all my life. Jock in school and pretty much in shape. I had a MI when I was 40. They had to hit me twice with the paddles to bring me back. I didn't know I had a "Heart Problem". I've been on rides all my life from Disney, 6 Flags...etc. So as far as the sign goes, not all are aware of "Heart Problems". That sign is for the people who are aware they do have the troubles and a warning. Just like the poor boy, and maybe this poor woman had no idea. Either way, I do not blame Disney, nor the woman if in fact she had no idea of her health.
How many of the people posting on this site have had catherization of the heart, or Stress Test to see if they have blockage or muscle damage to the heart? Those are actually the only ways of knowing if you have a heart condition. And not 100% mind you.
Sad to say, it's a very hard loss for her family and friends. My prayers go with them in this time.
Guy