The victory comes a week after Collins enjoyed the biggest win of her career, clinching the Miami Open 1000 hard court title and her back-to-back wins means she will move up to 15th in the world rankings.

Collins has announced that she will retire from the sport at the end of this season but has found herself playing in the form of her life and has extended her winning streak to 13 matches.

Kasatkina, the 2017 winner in Charleston, reached the final after a three-set semi-final win over top seed Jessica Pegula but Collins proved to be a step too far.

Collins, who defeated Greece's Maria Sakkari in her semi, needed just 77 minutes to defeat Kasatkina and the contest moved decisively in her direction when she broke to go 2-0 up in the second set, celebrating with a forceful first-pump.

The change in surface from Miami made little difference to Collins who marched to victory with her powerful strokeplay that was simply too much for the Russian.

Collins won 95.2% of first serve points and saved the two break points that she faced.

"I'm blessed to be able to have the opportunity to live out my dream, I am so grateful," said Collins.

Kasatkina joked that she was glad to know that Collins would be leaving the tour after this season.

"I was going to stay that I'm going to miss you on the tour but after this match, I'm not sure," she quipped.

"I am going to miss you because you are such a character, your personality is amazing. Enjoy these moments, you are playing amazing," she said.

The Floridian has dropped just two of 28 sets in her last two tournaments. The last player to win Miami and Charleston in the same year was Serena Williams in 2013.

Collins' 22 wins for the season is matched only by world number one Iga Swiatek and fourth-ranked Elena Rybakina.