Complex sentence: As a young girl Bly was often called "Pinky," because she so frequently wore the color, but as she bacame a teenager she wanted to portray herself as more sophisticated, and so dropped the nickname and changed her surname to Cochrane.
Split into simpler sentences: As a young girl Bly was often called "Pinky," because she so frequently wore the color. As she became a teenager she wanted to portray herself as more sophisticated, and so dropped the nickname and changed her surname to Cochrane.