She began 2010 with a win at the Lisbon Half Marathon, finishing with a time of 1:08:38. She improved her personal best at the Lille Half Marathon in September, running 1:07:48, but she was beaten to the finish line by débutante Florence Kiplagat. Arusei was selected for the 2010 IAAF World Half Marathon Championships as a result and she gained the bronze medal, forming the winning Kenyan team with Kiplagat and Joyce Chepkirui. Her 2011 season stated at the Paris Half Marathon and set a course record time to win the race. Making her debut over the distance, she led at the Vienna City Marathon for the first 30 km. However, she slowed in the heat and ended up in third place with a time of 2:27:17 hours. At the Amsterdam Marathon, she was among the mid-race leaders but yet again fell behind in the second half, ending the race in sixth place.