Tin foil would have been better
Bless her heart.
The plastic wrap may actually work, if applied correctly. But it won’t help against flooding.
I remember a couple of decades ago seeing images of farm land that was flooded by the Mississippi river overflowing. In it there was this huge shallow lake, and this one house surrounded by about a half acre of dry land around it. The owner had raised the level of the land before he built the house. It had not flooded.
This seems like a no brainer to me. If you are going to build in a flood plain, simply pay the extra money to bring in some dirt to raise up the places you plan on building to a level at least a foot higher than the highest ever flood and you should be pretty golden with that. It should affect your insurance rate as well.
I honestly don’t know why more people don’t do that.