I think you can return to her Manor after defeating the mage and read the diary there, which will allow you to progress on the brothel quest.
After you see the werewolf and get in “contact” with her, that is.
already read the diary. maybe that was the problem. also went back and was not allowed to return.
You can't softlock your quest by reading diary.
It shouldn't affect meeting the Werewolf. You need to meet the Werewolf (In heat) and fuck with her, or let Trudy handle her if you have high enough levels of scouting and stealth to sneak on her.
