After two baskets by Jones gave Tri-West a 60-58 lead with 1:45 to play, Mitchell drained a 3-pointer from the corner as she was being fouled.
She missed the free throw, but the Stars led 61-60.
Johnson gave Tri-West the lead 62-61 by hitting two free throws with 1:20 left, but Mitchell struck again 16 seconds later, getting loose on the backside for a lay-up to give the Stars the lead.
"We know that eventually BayLee is going to hit a big shot," Schelsky said. "I actually thought the one at the end of the second overtime was going in. She hit a big shot, she made some big plays and that is what you expect seniors to do. She hit shots that she needed to."
After getting a defensive stop, the Stars were able to run the clock down some before Chance was fouled with 14.9 seconds left. She made both shots to give the Stars a 65-62 lead and the Bruins never got a good shot for the tie, settling for an off-balance 3 by Jones in the waning seconds.
Mitchell finished the game with 16 points and 10 rebounds, while Chance had 10 points and seven rebounds. Kaitlin Miller had 12 points and 5 rebounds, while Rachel Ramey had nine rebounds.
The Stars will be back at it in a few hours, as they play Bishop Chatard at 8 p.m. at Danville.
Chatard defeated Owen Valley 83-48 in the other semifinal game.
"We are just going to get the kids home and rested," Schelsky said. "We came into this week expecting to play for a championship tonight and that is where we are at. We will talk Chatard when we get back and I think getting a game under our belts will help us tremendously. I think we will settle down, the nerves will calm down and the big thing is rest. That was a marathon game, Chatard had an easier time, but no excuses because at this point of the tournament you have to play with adreline and that is what we will do tonight. "