Valkenburg reached the quarterfinals of the singles event at the Australian Championships in 1931 which she lost to Joan Hartigan.

The pair reached the final where they were beaten by compatriots Emily Hood Westacott and Margaret Molesworth in three sets.

[2] In the mixed doubles event she reached the semifinal at the 1931 Australian Championships with Charles Donahue.

In January 1931 she was defeated in the singles final of the New South Wales Championships by Marjorie Cox Crawford.

[3] Valkenburg was a runner-up at the 1934 New South Wales Hard Court Championships, losing in the final in three sets to Iris Luckie.