Hunter Biden’s sister-in-law-turned-lover Hallie Biden testified Thursday that the first son introduced her to crack cocaine in the summer of 2018 and she was “embarrassed” and regretted “that time of my life.”

Hallie, the widow of Hunter’s late brother, Beau Biden, also told a federal court why and how she threw out the .38-caliber revolver prosecutors say Hunter illegally bought and owned — before undergoing a withering cross-examination by defense attorney Abbe Lowell.

Hallie — testifying under the promise of immunity — recalled the pivotal moment she found Hunter’s gun on Oct. 23, 2018.