WTF? They were not "lovers". They had a mutual weekend fling where both sides at the beginning knew where they stood. The Michael Douglas character did not hide his marital status. The screenwriters broke the plot of the movie by hammering the square peg "#MeToo" into the round hole.
This remake might be closer to the original storyline Glenn Close has talked about. She said her character was supposed to be an obsessed woman who’s a danger to herself. Originally, she was supposed to kill herself and frame him. When she was called back to redo the ending, she argued against it, but obviously she went along with the redo.
IMHO, the movie ending was perfect because the one solid, good person (the devoted wife) saves the day - after her sneaky husband put their family in danger by fooling around with a woman who turned out to be seriously disturbed.