Flushing Meadows semi-finalist Vandeweghe takes on Karolina Pliskova in Sunday's final after the fifth seed beat Estonia's Anett Kontaveit 6-4 6-2.
Asked about her success in Stuttgart on a clay surface that she has previously stated a dislike for, Vandeweghe said: "My mom told me I have some German heritage from my great grandmother so that's probably why it's clicking here.
"I'm definitely trying different things and enjoying my time out on the court instead of taking it too seriously. It's chill. It's like I'm back in California on the beach and I don't care."
Vandeweghe won her first break with the scores at 4-4 before serving out for the first set.
Garcia held firm up to 2-2 in the second but despite her best efforts, the sixth seed could not stop Vandeweghe from running away with the match.
Vandeweghe has beaten former world number one Pliskova three times in five career meetings but the Czech prevailed in straight sets when they faced off in the last 16 in Stuttgart last year.
(Reporting by Shrivathsa Sridhar in Bengaluru, editing by Pritha Sarkar)
