Collins, will face fourth-ranked Elena Rybakina in Saturday's final. The Kazakhstan player was pushed all the way by veteran Victoria Azarenka before coming out with a 6-4, 0-6, 7-6(2) victory.
Collins denied this week that her great run to the last four was a result of her playing with freedom after announcing her intention to retire at the end of this year.
But once again the American looked relaxed and in control as she took full charge of the contest against Russia's Alexandrova, who had beaten world number one Iga Swiatek in the fourth round before downing fifth-seed Jessica Pegula of the United States.
"It's even more special coming in my home state," said Collins, who hails from St. Petersburg near Tampa.
"I've had a couple of good years here, but this is definitely the most memorable," she added.
Alexandrova broke early in the first set but Collins swiftly got the contest back on serve before breaking again to go 4-2 up and take the set.
The American then broke on Alexandrova's first service game in the second and ran away with the set to complete a 74-minute victory.
"I've followed all of her matches this tournament, it was fun watching her because we have a very similar game style. It is tricky when it is like that," said Collins.
"That forced me to concentrate harder, react faster and really forced me to play up at my highest level," she said.
