Question: In the 2013 Citi Open – Women's Doubles, Aoyama successfully defended the title alongside Vera Dushevina, defeating Eugenie Bouchard and Taylor Townsend in the final, Bouchard is a Canadian professional tennis player, and became the first Canadian-born player representing Canada to reach the finals of a Grand Slam in singles, finishing runner-up to who?
Context: The Williams sisters are two professional American tennis players: Venus Williams (b. 1980), a seven-time Grand Slam title winner (singles), and Serena Williams (b. 1981), twenty-three-time Grand Slam title winner (singles), both of whom were coached from an early age by their parents Richard Williams and Oracene Price.  There is a noted professional rivalry between them – between the 2001 US Open and the 2017 Australian Open tournaments, they met in nine Grand Slam singles finals.  They became the first two players, female or male, to play in 4 consecutive grand slam singles finals from the 2002 French Open to the 2003 Australian Open; Serena famously won all 4 to complete the first of two "Serena Slams".  Between 2000 and 2016, a 17-year span, they collectively won 12 Wimbledon singles titles (Venus won 5 and Serena won 7).  By winning the 2001 Australian Open women's doubles title, they became the 5th pair to complete the Career Doubles Grand Slam and the only pair to complete the Career Doubles Golden Slam.  At the time, Venus and Serena were only 20 and 19 years old, respectively.  Since then they have gone on to add another two Olympic gold medals in the 2008 Beijing Olympics and the 2012 London Olympics.  Nearly a decade later, the duo would go on to win 4 consecutive grand slam doubles titles from 2009 Wimbledon through 2010 Roland Garros, which would catapult them to co-No.  1 doubles players on 7 June 2010.  Two weeks later, on 21 June 2010, Serena would hold the No. 1 singles ranking and Venus would be right behind her at No. 2 in singles.  Their most recent grand slam doubles titles came at the 2012 Wimbledon & 2016 Wimbledon events.  They remain very close, often watching each other's matches in support, even after one of them has been knocked out of a tournament. Eugenie "Genie" Bouchard (born February 25, 1994) is a Canadian professional tennis player.  At the 2014 Wimbledon Championships, Bouchard became the first Canadian-born player representing Canada to reach the finals of a Grand Slam in singles, finishing runner-up to Petra Kvitová.  She also reached the semifinals of the 2014 Australian Open and 2014 French Open, and won the 2012 Wimbledon girls' title.  Following the end of the 2013 WTA Tour, she was named WTA Newcomer of the Year.  The next year, Bouchard received the WTA Most Improved Player award for the 2014 season. Filip Peliwo (born January 30, 1994) is a Canadian professional tennis player.  Peliwo became the first Canadian male and second Canadian ever to win a Grand Slam in singles at any level with his 2012 Wimbledon boys' title win.  This was Canada's second Grand Slam title in two days, one day after Eugenie Bouchard's.  With the victory, Peliwo reached the No. 1 combined junior world ranking in July 2012, the first time a Canadian has been top ranked.  He won his second straight junior Grand Slam title at the 2012 US Open.  Peliwo was also runner-up in the boys singles events at the 2012 Australian Open and French Open. Kenneth Robert Rosewall {'1': ", '2': ", '3': 'AM, MBE', '4': "} (born 2 November 1934) is a former world top-ranking amateur and professional tennis player from Australia.  He won a record 23 tennis Majors including 8 Grand Slam singles titles and before the Open Era a record 15 Pro Slam titles and a record 35 Major finals overall.  He won the Pro Grand Slam in 1963.  Rosewall won 9 slams in doubles with a career double grand slam.  He is considered to be one of the greatest tennis players of all time.  He had a renowned backhand and enjoyed a long career at the highest levels from the early 1950s to the early 1970s.  Rosewall was one of the two best male players for about nine years and was the World No. 1 player for a number of years in the early 1960s.  He was ranked among the top 20 players, amateur or professional, every year from 1952 through 1977.  Rosewall is the only player to have simultaneously held Pro Grand Slam titles on three different surfaces (1962–1963).  At the 1971 Australian Open he became the first male player during the open era to win a Grand Slam tournament without dropping a set. This is a list of the main career statistics of professional Canadian tennis player, Eugenie Bouchard.  To date, Bouchard has won one WTA singles title at the 2014 Nuremberg Cup.  Other highlights of Bouchard's career thus far include a runner-up finish at the 2014 Wimbledon Championships, semi-final appearances at the 2014 Australian Open and 2014 French Open and a quarterfinal run at the 2015 Australian Open.  Bouchard achieved a career high singles ranking of World No. 5 on October 20, 2014. Shuko Aoyama and Vera Dushevina were the defending champions, but Dushevina chose not to participate.  Aoyama successfully defended the title alongside Gabriela Dabrowski, defeating Hiroko Kuwata and Kurumi Nara in the final, 6–1, 6–2. Eugenie Bouchard and Taylor Townsend were the defending champions.  However, Bouchard was no longer eligible to compete in junior tennis, and thus could not defend her title.  Townsend chose not to defend her title, deciding instead to only compete in singles. Shuko Aoyama and Chang Kai-chen were the defending champions but Chang chose not to participate.  Aoyama successfully defended the title alongside Vera Dushevina, defeating Eugenie Bouchard and Taylor Townsend in the final, 6–3, 6–3. Li Na (; ; born 26 February 1982) is a retired Chinese professional tennis player, who achieved a career-high WTA-ranking of world No. 2 on 17 February 2014.  Over the course of her career, Li won seven WTA singles titles and two Grand Slam singles titles at the 2011 French Open and 2014 Australian Open.  Li's rise to prominence came after those victories, which made her the first and only Grand Slam singles champion from East Asia and Asia as a whole.  Prior to this, she had already become the first player representing an East Asian and Asian country to appear in a Grand Slam singles final, a milestone she achieved at the 2011 Australian Open.  Li was also the runner-up at the 2013 Australian Open and 2013 WTA Tour Championships, a three-time quarterfinalist at Wimbledon and a semifinalist at the 2008 Beijing Olympic Games and 2013 US Open.  Among her other most notable accolades, she was the first Chinese player to win a WTA tour title at the Guangzhou International Women's Open in 2004, the first to reach a Grand Slam singles quarterfinal at the 2006 Wimbledon Championships, and the first to break into the world's top 10.  Her feats have sparked a major population growth of tennis players in East Asia, earning her the reputation as the region's tennis pioneer and trailblazer. The 2013 Citi Open (known as such for sponsorship reasons) was a tennis tournament played on outdoor hard courts.  It was the 45th edition (for the men) and the 3rd edition (for the women) of the event known that year as the Citi Open (previously known on the men's tour as the Legg Mason Tennis Classic), and was part of the ATP World Tour 500 series of the 2013 ATP World Tour, and of the WTA International tournaments of the 2013 WTA Tour.  It took place at the William H.G. FitzGerald Tennis Center in Washington, D.C., United States, from July 27 to August 4, 2013.
Answer: Petra Kvitová