Her score was a shot better than 15-year-old Lydia Ko, the top-ranked amateur in the world.
Ko, of New Zealand, is the youngest player ever to win a professional tour event and is ranked 25th in the world. She has won once each on the Ladies European Tour and the LPGA Tour, and twice on the Australian Ladies Professional Golf Tour.
Ramsey also beat No. 1-ranked Stacy Lewis (73) and No. 2 Yani Tseng (72).
WEB.COM TOUR: In Sao Paulo, Richard S. Johnson, Danny Lee and Tom Hoge all posted 6-under-par 65s to share the first-round lead at the inaugural Brasil Classic.
The three are one stroke better than veteran Carlos Franco, Kelly Kraft, Lee Bedford, Zack Miller and local favorite Rafael Barcellos.
The Sao Paulo Golf Club course measures only 6,574 yards and the field took advantage of the shorter holes as 76 players broke the par of 71.
Another 15 players – including Alex Rocha of Sao Paulo and host pro Erik Andersson – are packed together at 67. Fifteen more are in at 68, which puts 38 players within three shots of the lead.