How does Olivia end up leaving Angier?

Angier states that he and Olivia no longer share a love, but more cling to one another out of necessity. Olivia offers to apply to be Bordon's assistant, find out his secret, and bring it back to Angier. Oliva applies using her mother's maiden name, Westcombe, and is hired. She grows distant from Angier and eventually send her maid to collect her belongings from him. She meets with him just one last time and hands him an envelope with the word 'Tesla' printed inside. She says this is Bordon's secret.