Why was the journey special to Sacagawea?

During the Lewis and Clark, expedition, Sacajawea, their Shoshone interpreter, received a shock. Sacajawea had been kidnapped from her village by a warring tribe when she was still a child. She subsequently had been given to a French trader, who she married, and had just given birth to a little boy. Upon entering a Shoshone camp for supplies, she found out that the chief of this particular tribe was her brother.