Even with the invisibility spell Whisper cast on her?
Unfortunately yes. It's able to hear her, so it knows she's here. being invisible simply means it'll have a harder time actually hitting her, but regardless it's aware of her presence now. Still it's not entirely useless since it only has a general knowledge that Yin is here, and if she can get far away enough from it it'll lose her trail. But right now Yin is too close, and also her stealth roll was unfortunately not enough to beat the monster's passive perception, taking into account it's keen senses.
It's only if Yin herself does something, similar to how invisibility would work in a normal party comp. As long as she doesn't attack or cast spells she'll remain invisible.
Posted: If we do enter initiative before I can formally hold an action, then consider that my action when it gets to my turn in the pass; to hold and swing if it enters reach.