That is exactly what happened.
Fortunately, I saved my game just before speaking with her, so after a reload it worked, when I kept the route to the cupboard clear.
Yet, I deem it a bug because, if I hadn't saved just before, I would have had to replay a portion of the game, losing the things that I had achieved until that point.
I am more concered, however, about not being able to provide the extra service. Hopefully, someone can tell me how to activate it again, or how to give the signal to express my readiness?