Said woman seems to be a high level mage or even a high level Goddess. She was able to put to sleep lots of people and set last ep monster to target Bell.
I think she's more than capable to either manipulate/spell Syr into giving the grimoire to Bell alone and/or cast a spell on the grimoire so that it only falls into Bell's hands in the end.
Some kind of invisibility spell where an object feels useless or does not catch the interrest of anyone but the target.