The American, who bested former world No. 1 Jelena Jankovic in last year's Birmingham finale, was bounced 6-3, 6-1 by Croatian qualifier Ajla Tomljanovic in the first round of the Wimbledon tuneup.
The news was better for world No. 42 Jamie Hampton of the United States, however, who advanced with a 6-2, 6-3 upset of 10th-seeded Taiwanese Su-Wei Hsieh at Edgbaston Priory Club.
Another seeded player falling by the wayside Monday was No. 11 Ayumi Morita of Japan, who fell 6-4, 6-0 to Belgian qualifier Alison Van Uytvanck.
Meanwhile, No. 13 Bojana Jovanovski of Serbia got past Canadian Eugenie Bouchard 5-7, 6-3, 6-2, and 16th-seeded Slovakian Magdalena Rybarikova breezed by British wild card Melanie South 6-4, 6-2.
American Madison Keys, Bulgarian Tsvetana Pironkova, Czech Kristyna Pliskova and U.S. qualifier Alison Riske also posted wins.