Second-seeded Julia Goerges saved a match point but was upset by Kristyna Pliskova.
The other semifinal features the Czech Republic taking on Germany.
The 23-time Grand Slam champ is 19-2 in her career against the Russian.
The Dutchwoman won two matches on Sunday to claim her fifth career clay-court title.
Williams takes on Julia Goerges; Rafa will try to go to 16-0 against Richard Gasquet.