where in the diaries? *spoiler*

Actually, according to the official Anais biographer Deirde Bair's book called "Anais Nin" things played out similarly to the movie plot.

June was told by Michael Frankel, Miller's expatriate American friend in Paris, about Anais being his patron and mistress. She came to Paris, the two women developed intense friendship and tried to seduce each other as a way of diffusing attention from Henry and as a masked competition. The after party bedroom scene happened in reality in much the same way. June passed out drunk and Anais just watched her fully clothed. Henry was asleep and afraid to check the situation in fear what he'd see. The next morning June confronted him telling she put on a lesbian act to trap Anais into telling her the truth about the two of them. She demanded a divorce and, as legend grew around this incident, supposedly said to Henry "Now you have the last chapter for your f----g book".

There was more drama later but the movie skipped the part of June threatening them with bodily harm and taking money from Henry's wallet, him escaping to London just to be turned back by the British customs and other details. Basically he let June go to Anais's delight. She later abandoned him after engaging in an incestuous affair with her father.

I hope this helps.