In a repeat of last year's final which Sevastova lost, the Latvian defeated No. 23 Caroline Garcia 6-4, 6-2 but didn't have it all her own way.
She fell 2-0 down in the opening set, with Garcia breaking serve in the second game, before gaining her composure to win the next four games and holding serve to win the set.
Sevastova broke serve in the opening game of the second set and cruised into her second consecutive final.
In the opening semifinal Julia Goerges powered her way past American Catherine Bellis 6-1, 6-1, breaking the teenager's serve on six occasions.
It will be Goerges seventh appearance in a WTA final, but her first on grass as she goes in search of her third career title.