But her injury has unified the team on the eve of the regatta at the Youth Olympic Games and they are rallying round to help her.
"It sounds silly, but I slipped on wet concrete a couple of weeks ago and that was that."
"We're so close knit that I just wanted to come, even though I'm in a wheelchair and on crutches."
She was forced to weave through the boat yard in her wheelchair and dictate team movements from the sidelines.
Tierney said: "The hardest part is going up stairs; it seems as if they are everywhere, but everyone has been helping me."
Even though she is restricted by her injury, her presence is still important to the team.
Coach Grand Poiri (COK) said: "We need her because she pushes us. Even though she broke her leg, she's still with us. It shows that she really cares and has a lot of belief in us."
Byte sailor Aquila Tatira (COK) said the team has been doing their best to accommodate Tierney's injury.
The 16-year-old said: "We push her around and make sure she does not crash, and we also help her up stairs whenever we can."
The Cook Islands sailing team has high hopes at the National Sailing Centre. Poiri said: "We came to win gold, but we're also here for the great experience."
For full details on the Sailing competition at the Youth Olympic Games visit: www.sailing.org/yog