They outscored the Thunderbirds in the second term, 13 goals to eight.
This put them 21-20 ahead at the main break at Netball SA Stadium.
The Vixens shut off Adelaide's mid-court run throughout the match and defenders Geva Mentor and Bianca Chatfield suffocated Thunderbirds goalies Erin Bell and Carla Borrego.
Characteristically, the home side were not going to give up and, led by captain Nat von Bertouch, the Thunderbirds fought back hard in the final quarter.
An intercept by goalkeeper Sharni Layton handed Adelaide the momentum and helped her team to a 10-goal win.
Adelaide will have a break this week while Melbourne Vixens will face the winner of last night's minor semifinal between Waikato Bay of Plenty Magic and Queensland Firebirds.