"Dan, it's your made up magic system. You could just say she can chose not to shrink the jacket."

NO THAT'S NOT HOW IT WORKS!

"She's awakened. She could have a spell that shrinks everything with the option to intentionally exclude something."

BUT SHE DOESN'T HAVE THAT!

"You could write it so she does."

NO! SHE WOULDN'T HAVE THAT AT THIS POINT!

"Okay...???"

In all seriousness, with a system like EGS's, pretty much any spell could be excused, but I don't think pretty much any spell SHOULD be excused.

Granted, that shrink everything but exceptions are allowed spell makes sense. She might get that someday, but not THIS day! In part because it would cause a time paradox, as I'm pretty sure this exact incident is why she would get that spell in the first place.

Although it could just be an upgrade to the shrink spell... As a result of this incident. No, it still has to be something she gets after because of wibbly wobbly time stuff.