The meeting lasted 2 hours 32 minutes and ended with the score 4:6, 6:1, 3:6.
The Russian woman made five double faults, converted nine out of 14 break points and never filed right through.
The Spaniard made one ace, converted nine break points out of 17 and made five double faults.
In the 1/4 finals of the tournament, the representative of Spain will play with the winner of the pair Jessica Pegula (USA) - Bianca Andreescu (Canada).
Earlier it was reported that Russian Ekaterina Alexandrova defeated Czech Maria Bouzkova in the third round match of the WTA tournament in Madrid.