The triumph made up for Mantilla's four-set defeat last year at the hands of Albert Costa. He said: "In 1996, I was not consistent, especially after I lost the second set. This year I was strong physically and mentally." The result underlined Spanish domination at Gstaad, with six wins in the last seven years.
France, under Yannick Noah's captaincy, reached the final of the Fed Cup after beating Belgium 3-2 in Nice thanks to a 3-6, 6-2, 7-5 victory for Nathalie Tauziat and Alexandra Fusai in the decisive doubles against Els Callens and Laurence Courtois.
For France, who were without Mary Pierce who pulled out with a sore right arm, it is their first final after seven semi-finals. They will meet either the Czech Reoublic or the Netherlands.
Meanwhile in Australia, the Spanish women, Arantxa Sanchez Vicario and Maria Luisa Serna, won their reverse singles matches to lift their country to a 3-2 victory over Australia in their Fed Cup world group play-off at Hope Island. The win means Spain stay in the elite eight-nation world group next season while Australia must remain in group two.