The first four penalties had gone to her left.
Jones guessed right, made the save and Kendall Fletcher held her nerve to punch Canberra's ticket to the W-League grand final.
United beat the Victory 5-4 in a penalty shootout in Saturday's semi-final at Geelong's Simonds Stadium after there were no goals in regulation or in half an hour of extra-time.
United will now play the winner of Sunday's semi-final between minor premiers Perth Glory and Sydney FC as it tries to collect its second W-League championship and first since 2011-12.
The grand final will be held at Viking Park next Sunday if Sydney FC can upset the Glory.
Jones said she always knew she would stop at least one of the penalties after both teams went a perfect four from four to start.
"I knew I had to stay focused even if I missed the first few and guessed wrong," Jones said.
"All the penalty kicks they had taken had gone to my left, so I was going left and we'll see what happens.
Fletcher did just that, the midfielder slotting her kick into the bottom left corner of the net past Victory's impressive goalkeeper Brianna Davey.
"This is my contribution," Fletcher said.
"I wanted to take that responsibility on my shoulders.
The irony is Fletcher won't be allowed to play in the grand final.
With the three full-time import spots filled by fellow Americans Jones, Lori Lindsey and Stephanie Ochs, Fletcher is the team's designated guest player who is allowed seven games for the season.
Saturday's semi-final was number seven.
She started her contract a week early, helping United to a crucial 1-0 win against the Victory in round seven.
"Soccer's a team sport and sometimes your number's called and sometimes it's not," Fletcher said.
"I'd love to be out there with the girls but I've got no doubt in my mind that they're going to go out there and do everything they can to win the thing.
"My job next week will be to cheer them on."
United had plenty of chances to score, starting in the opening five minutes when Ashleigh Sykes couldn't get a foot on a great ball from Michelle Heyman.
Matildas striker Heyman got herself in great positions, continually troubling the Victory defence but unable to capitalise.
Heyman went within a whisker of scoring the winner in the 88th minute but her header bounced off the side of the goalpost.
She had another chance with the last kick of the game but put her shot straight into the waiting arms of Davey.
United defender Ellie Brush played the entire 120 minutes after going into the game with an ankle injury.
W-League: Canberra United 0 d Melbourne Victory 0 (5-4 on penalties) at Simonds Stadium on Saturday.