The Romanian just edged a hard-fought clash with Lucie Safarova 7-6 (7-5) 1-6 6-3, while Pavlyuchenkova reached her second final of the year with victory over Katerina Siniakova.
Begu immediately put fourth seed Safarova under pressure in the fourth game of their semi-final, saving three break points to hold, but was struggling to make any inroads on Begu's serve, only winning nine points in the set.
As both continued to hold a tie-break was inevitable, Begu made a quick start to take the opening three points and although Safarova tried to come back a third mini-break enabled the Romanian to take the set.
The Czech immediately put that disappointment behind her, though, to win the opening five games of the second set as Begu lost all momentum.
Safarova saw two set points go by when 5-0 up, before serving out to love to level the match.
Both players started the deciding set well before Begu claimed the crucial break in the eighth game, booking her first final of the season.
She will meet sixth seed Pavlyuchenkova in Sunday's final after she overcame the challenge of Siniakova, winning 6-2 6-2
The 18-year-old started slowly as Pavlyuchenkova took the opening two games, but she continued to battle throughout the set, not giving her opponent any easy points.
Eventually Pavlyuchenkova broke again with her fourth chance of the set, and she secured a 1-0 lead with a solid service game.
The second was much easier for the world number 30 as her young Czech opponent struggled to find her shots, Pavlyuchenkova breaking twice more to reach the final.