Tirfi was runner-up to Atsede Baysa at the 2010 Paris Half Marathon,[8] then finished behind her again at the Paris Marathon a month later, although Tirfi's time of 2:24:51 hours for third place was a significant personal best.[9] She again made the podium at the Toronto Waterfront Marathon, setting another best of 2:22:44 hours and finishing second behind Sharon Cherop.[10] She was also runner-up at the Shanghai Marathon for the second year running, beaten to the title by Nailiya Yulamanova.[11]
She was invited to compete at the 2011 Boston Marathon and she finished in eleventh in the high-profile race.[12] She came fifth at that year's Lille Half Marathon then was three seconds behind Shanghai Marathon winner Haile Lema Kebebush in December with her time of 2:24:11 hours (her third straight second-place finish at the race).[13] At the Roma-Ostia Half Marathon in February 2012 she ran a personal best of 1:07:42 hours for third place.[14] She was the pre-race favourite for the Paris Marathon and delivered on the status by winning the race in a course record and personal best time of 2:21:39 hours, over three minutes ahead of runner-up Sultan Haydar.[15] Running alongside her training partner, Aberu Kebede, she was runner-up at the 2012 Berlin Marathon with a personal best time of 2:21:19 hours.[16]
In January 2013, she won the Dubai Marathon despite the heavy fog during the race, with a time of 2:23:23, 16 seconds ahead of runner-up Ehitu Kiros.[17] She performed less well in her second race of the year, coming seventh at the Frankfurt Marathon in 2:26:57 hours.[18]
She won the 2014 Berlin Marathon, held on 28 September 2014, in a personal best time of 2:20:18.[19]