Aren't crusty old librarians who don't seem to like children a rite of passage? : the Librarians here.
But, if they want children to become literate, they need to accomodate them in the library. They don't tell little kids to be quiet in the arcade or game stores.
Wow, she's a live wire.
If your dh, bless him, is on board, I'd have him talk with her preferably privately.
She really needs to respect the fact that you (both you and dh,) are adults and have the right to run your family as you see fit.