From the Super Mario Wiki
Mrs. President was the First Lady of the United States during The Adventures of Super Mario Bros. 3, and is the wife of Mr. President. An animated version of her appeared in The Adventures of Super Mario Bros. 3 episode "Reptiles in the Rose Garden". In reality, the title of Mrs. President is currently held by Michelle Obama.
In the episode, King Koopa used a Levitation Beam to warp the White House, along with everyone inside (including Mrs. President and her husband) to Dark Land. Shortly afterwards, Bowser banished the White House to the bottom of the Mushroom Sea. Mrs. President feared for their lives, while Mr. President simply continued his phone conversation.
When Mario showed up wearing a Frog Suit, Mrs. President was frightened of him at first. However, Mario quickly proved himself to Mrs. President by flushing the water out of the partially-flooded White House, allowing it to rise to the surface of the Mushroom Sea. As a thank you, Mrs. President told Mario that her husband would recommend him to all of their friends.
When Mario managed to warp the White House back to Washington, D.C., he accidentally placed it on top of the Washington Monument. Mrs. President told Mario that her husband couldn't run the country like this. Although she was never seen again on the show, it's assumed that her life returned to normal once the White House was returned to its proper spot.