Five years before Kitty knew Sherlock she was kidnapped by a man and a victim of rape. She now lives under an assumed name to try and escape her past. Kitty tells Joan Watson that when she met Sherlock in London, she was at a low point in her life.
After becoming Sherlock's protégée and moving to New York City with him she agrees to go to a support group for rape victims. However, Kitty tells Joan that she is only doing this to gain Joan's future help because she knows that Joan feels that it is important.
She has a lot respect for Sherlock.
Kitty leaves New York, and returns to London. She tells Sherlock that she loves him.