By default Divi includes this right border in sidebars (widgets):
Divi Right Side Bar Border
I find myself removing it on every install; so I finally added it to my default installation child-theme style.css file and am capturing the css required to remove it.
Divi Right Side Bar Border Removed
Native Texas, Logan Seth Ramirez is a computer science graduate from Trinity University and lives in San Antonio with his wife and four children. Along with being a web hero, he authored The Groom Wore White Socks, sings and songwrites as Logan Seth, and his favorite Spanish word is cacahuates.