She took a cross country circuit wins at the Cinque Mulini in 2003 and the Oeiras International Cross Country in 2004. At the 2004 IAAF World Cross Country Championships she just missed out on the medals by finishing in fourth place behind Werknesh Kidane, although she did lead the Kenyan women to a team silver medal in the long race. She took to the Olympic stage for a second time later that year, but she failed to build on her cross country success at the 2004 Athens Games and finished in sixteenth place in the 10,000 m Olympic final. She delivered in the long race at the 2005 IAAF World Cross Country Championships the following year, however, as she edged between Tirunesh Dibaba and Werknesh to take her first major senior medal, and also leading Kenyan to a consecutive team silver behind Ethiopia. Returning to the track, she ran at the 2005 World Championships in Athletics but did not manage to finish the race, repeating her disappointing World performance of six years earlier.
Focus on road running
Timbilil won the Saint Silvester Road Race in 2007, running 15 km in 53:07. At the 2007 IAAF World Road Running Championships she finished in ninth place. She made her marathon debut at the 2008 Paris Marathon and she set a time of 2:26:45 for fifth position. Her first major race of 2010 came at the Roma Ostia Half Marathon in February, which she won in a time of 1:10:34, beating home favourite Rosaria Console. Timbilil took part in the 2010 BIG 25 road race in Berlin in May and took second place with 1:24:38, although this was over three and a half minutes slower than Mary Keitany who set a world record. She took on Keitany at the Portugal Half Marathon and was second best again, although she beat the rest of the field by some twenty seconds. At the 2010 Amsterdam Marathon, she was among the leaders from the start and by the 35 km mark she had outrun the field, eventually winning the race by a margin of two minutes with a personalbest of 2:25:03. She ended the year by setting a course record at the Saint Silvester Road Race. In 2010, she not only won her first marathon, but had improved all her personal bests over 10K, 15K, 25K and the marathon. She was runner-up at the Goyang Half Marathon then placed eighth at the 2011 Boston Marathon the following month. In July she was runner-up at the Peachtree Road Race and winner of the Boilermaker Road Race, but did not compete again until late 2013. After a runner-up finish at a half marathon in Kisii she returned to the major circuit with a third-place finish at the Amsterdam Marathon.
Personal life
She is married to Mark Sinyei and she gave birth to their first son, Collins Kimutai, in March 2006. She comes from an athletic family which includes runner and African Champion Nancy Lagat – her aunt. Timbilil is managed by Federico Rosa and is based at the Nike camp in Kaptagat. She comes from the same village as another female runner Vivian Cheruiyot