You don’t think she knew it was coming? Its called “Acting.” She knows that whenever anyone sees her, thats the first thing they think of. She was a good sport for taking part in that way.
That’s an unknown. With skits, the players are often just given an outline of script and then allowed to use their instincts to act out on the fly. Consequently, unintentional things are said or done and everybody rolls with it. SNL skits are like this. Many of their minor skits were improvisations done from a bare script.
Second, even if they were given a complete script with a complete dialogue, actors will often Change a line because they think it might work better.
Third, they are still real people with real feelings. Showgirls killed Berkeley’s career for almost 15 years. Though she may have been fine having done the movie, having people snicker about it since has probably created some negative feelings about it. It’s one thing to read it in the script, but then to have the rubber hit the road and have the words actually said can still be a bit of a shock.
You could also be correct in that Berkley wanted to use that moment to let the world know she was passed it.