Liz had no objections to JoAnna assisting her. By working together, Liz will get closer to JoAnna.
Since Liz is working at the Franciscan Medical Center (JoAnna's previous workplace), Liz heard stories about a young surgeon who caused waves before leaving.
Liz also remembered that the White corp. was one of the major donors to the Franciscan Medical Center, and shortly after Liz joined, the White corp. redirected their money to other institutions. Seeing Jeff with JoAnna, Liz understood that it was the case of a husband supporting his wife. Just how Max is supporting her.