Question: Was Kristie Boogert or Alex O'Brien ranked higher as a singles player?

Context paragraphs:
Alex O'Brien: Alex O'Brien (born March 7, 1970 in Amarillo, Texas) is a retired professional tennis player from the United States, who competed on the ATP Tour.  He became the world No. 1 doubles player in May 2000 and was ranked as high as world No. 30 in singles in June 1997.

1996 Wilkinson Lady Championships – Doubles: Larisa Neiland and Brenda Schultz-McCarthy won in the final 6–4, 7–6 (9–7) against Kristie Boogert and Helena Suková.

1997 SEAT Open – Doubles: Kristie Boogert and Nathalie Tauziat were the defending champions but only Boogert competed that year with Amanda Coetzer.

1995 Schweppes Tasmanian International – Doubles: Linda Harvey-Wild and Chanda Rubin were the defending champions but they competed with different partners that year, Harvey-Wild with Leila Meskhi and Rubin with Kristie Boogert.

Lorna Woodroffe: Lorna Woodroffe (born 18 August 1976) was an English Olympic tennis player.  Lorna competed in the 2000 Summer Olympics in Sydney, Australia.  Playing with Julie Pullin, Lorna lost her first-round match in the Women's doubles to Kristie Boogert and Miriam Oremans of the Netherlands, in two sets.

1996 SEAT Open – Doubles: Kristie Boogert and Nathalie Tauziat won in the final 2–6, 6–4, 6–2 against Barbara Rittner and Dominique Van Roost.

1997 Sparkassen Cup – Doubles: Kristie Boogert and Nathalie Tauziat were the defending champions but only Boogert competed that year with Amanda Coetzer.

2000 Australian Open – Mixed Doubles: Mariaan de Swardt and David Adams were the defending champions but only Adams competed that year with Kristie Boogert.

1997 Open Gaz de France – Doubles: Kristie Boogert and Jana Novotná were the defending champions but they competed with different partners that year, Boogert with Irina Spîrlea and Novotná with Martina Hingis.

Kristie Boogert: She has not won any singles titles, but did win three titles in doubles.  At the 1994 French Open championships she won the mixed doubles title with countryman Menno Oosting.

Supporting paragraphs: Kristie Boogert Alex O'Brien
Answer: No. 30 in singles