"People have been talking about this ever since the day after the movie came out."
I don't think that timeline is accurate. People who saw the film may have discussed this with others, but I didn't know about this until the flap about Medved and some others revealing the ending started. That was weeks, for sure, after the film opened. Roger Ebert loudly critized Medved for revealing the ending, indicating that he (ebert) and many others had reviewed it without revealing this plot twist.
So if this woman saw the movie right when it came out, even in the first week or two, she may well have been surprised by the ending.
I never go to the movies, but I do keep up with the reviews!
No, that was the stink by Ebert about the ending being revealed by a movie critic (Medved) and by Rush. But really word was out in the public as soon as it hit the theaters, because people were talking.
I also recall from the beginning that it was advertised as a drama about life, death, and choices. It was clear that it was about a boxer who was facing her own mortality. While it wasn't clear that it involved assisted suicide, even the casual movie goer should have had plenty of hints from the ads that it wasn't an uplifting Rocky-type movie.