Presumably someone fully encased in silver cloth, wouldn’t be able to use any magic either, so if Georgine comes at them with silver cloth, she won’t be able to get past the physical door. And if she takes off her silver cloth to deal with the door, the barrier will make sure they won’t be blasted to bits by whichever attack takes out the door and hopefully buy enough time for knights to react to the commotion.

Sure against a determined attack, the barrier won’t hold for long (especially with how it was charged by two people with mana capacities of lower-end med nobles), but Georgine is in a hurry, so just a small speedbump in and off itself might already be the difference between her tackling a potential inconvenience immediately or bypassing it for now on her way to the foundation.

And even if it’s entirely ineffective, it at least helps to keep the people inside of it calm and out of the way, should a fight between Georgine and some knights break out, if nothing else.