In the semi-final in Guadalajara, Mexico, Garbiñe Muguruza defeated her compatriot Paula Bardosa in two straight sets - 6-3, 6-3.
The two-time grand slam winner will now face Estonian Anett Kontaveit in the final.
- I am very happy, I lost my first match in the group stage (Karolina Pliskova) and was already looking for a flight home, Muguruza says after the semifinal against Bardosa.
The finalists also met in the group stage, when Muguruza won 2-0 in sets.
It is Kontaveit's only loss in the tournament, she then defeated world number two and world number three Barbora Krejcikova and Karolina Pliskova - both from the Czech Republic - and in the semifinals she won against Greek Maria Sakkar with 2-1 in sets.