[budj]

"To flounder is (1) to struggle or move with difficulty, as in mud; or (2) to behave awkwardly or make mistakes. One who flounders does not fail completely but merely struggles. To founder is (1) to cave in, (2) to sink below the water, (3) to fail utterly, or (4) to go lame. While to flounder is merely to struggle, foundering usually involves utter failure."
https://grammarist.com/usage/flounder-founder/

Let her founder.

[luvbach1]

Founder and flounder are often used incorrectly. I think one of the reasons, aside from the similarity of the words, is that flounder does evoke an image of flopping around helplessly.