After 19-year-old Andreeva sealed a 6-1, 6-3 semi-final win over Ukrainian Marta Kostyuk, it was Chwalinska's turn to shine under the roof of Court Philippe Chatrier, and the 24-year-old delivered her best tennis when it mattered to go through.
"It feels like a dream. I don't know what's going on. I'm just ... I don't know what to say, I'm very happy," Chwalinska said to huge cheers from the Court Philippe Chatrier crowd.
"I'm not feeling great (physically), I won't lie, it's so challenging to play against the best players in the world day after day, but it's a Grand Slam and you have to give it your all and more.
"I'm not complaining at all."
Shnaider cut a frustrated figure in the opening set as her opponent came up with some stunning winners that showcased her power and precision, but the 22-year-old Russian hit back to recover a second break and draw level at 4-4.
Chwalinska turned up the style further in the battle of the left-handers, unleashing a backhand winner to hold in a marathon 11th game, before earning a set point in the ensuing tiebreak with the perfect lob.
The crowd favourite, playing in her ninth match at Roland Garros this year and sporting strapping on her left thigh, took the opening set to roaring applause before going toe-to-toe with Shnaider in the opening eight games of the next.
"I'm crazy sometimes, but I try to stay composed," she said of her calm approach in tense moments.
"It's the best way for me and helps me play my best tennis. I'm trying to do that, but inside there's a storm, believe me."
A decisive break in the next game gave Chwalinska a great opportunity to close out an absorbing contest in two sets, and the world number 114 stayed focused to finish her opponent off on her first match point with a forehand winner.
Saturday's final will crown a new Grand Slam champion and Chwalinska said she was ready to step into the spotlight and looked forward to her next clash.
"I watched Mirra's match a bit," added Chwalinska, only the second qualifier to reach a Grand Slam final in the professional era after Emma Raducanu's triumphant US Open run in 2021.
"Her game is incredible. It's another great experience for me. I'll give my all, it's a Grand Slam final."