The diminutive Italian is the first player from her nation to reach the final on the Paris clay since doubles partner Sara Errani in 2012, and her resounding victory came two days after compatriot Jannik Sinner made it to the last four in the men's draw, guaranteeing he would be world number one next week.
Paolini, who used her booming forehand to devastating effect on court Philippe Chatrier, will face the ultimate challenge in Iga Swiatek, after the world number one and two-time defending champion made light work of Coco Gauff in the other semi-final.
Andreeva, who had won her previous match against Paolini in Madrid in April, failed to make the most of the few opportunities she had, and made too many unforced errors to stand a chance in what was both players' first appearance in a Grand Slam semi-final.
"It was a tough match, she's playing unbelievable, she's 17 years old, she's so complete so I was a little bit nervous before the match," said the 12th seeded Paolini who will play in the doubles semi-finals on Friday.
"I lost against her one month ago so I was like, come on you have to do better, today I was nervous in the first set but then ball after ball I was getting relaxed...
"I learned I think a little bit later than other players maybe, to dream is I think the most important thing in sport and in life, I'm happy that I could dream this moment and I don't know what to say, I'm so emotional."
With Errani watching from the stands, Paolini peppered the court with forehand winners.
Andreeva, however, managed to keep her at bay with deep groundstrokes on her service games in a captivating start.
Paolini broke for 3-1 and staved off three break points to move 4-1 up. She saved another two in the seventh game before sealing the opening set on her first opportunity.
The Italian broke early in the second set and she never looked back, wrapping it up with yet another forehand winner on the first match point after Andreeva completely lost her way.