The first clue as to how not very good at her job she was can be seen in the first few minutes of the special "A Storm In April." As we all know, Elly did the very fool-hardy thing of assuming that even if April did actually move from the spot where she plopped her down, her co-workers would be only too happy to entertain her child while she did her super-impressive what-the-hell-ever despite having walked right by the sign saying that this was not the case every single working day for the last ten years. I might be a picky-faced hater but I think that if you can't remember that after a decade on the job, you're sort of out of it.
The second clue as to her incompetence as a librarian is her incompetence as a cashier. When she isn't whining about how unfair it is people are in as big a rush as she is, she's freaking out because she's behind the times, howling in despair because bookstores have coffee counters now, dealing with idiotic, lazy, thieving asskissers or losing her temper because customers don't like to have someone hover over them like a buzzard. In short, if there's a way to suck at her job, you can bet that Elly will find it.
This is why I've always wanted to write my own Liography for Deanna; in it, Mira would talk about the clueless twerp librarian who was as much help as a screen-door in a submarine.