It's not a librarian's job to look after your children. Why would you do this? Would it be ok if I dumped some kids you don't know off at your office without telling you where I was going or when I would be back? It is not in their job description!
You do see a library as a crèche, clearly you do, because you're saying if she gets into trouble the librarian won't mind sorting it out. I'm telling you they will mind, very very much. You're about to leave your CHILD there without signing her in with anyone, without any information given to an adult, and just hope that things will be ok. Wow. Librarians are not teachers, they don't have in loco parentis status.
It's a large city centre branch
Yes, those ones are always the safest..... Arrgghhhh!!!!!!!!
You are being so incredibly naive! Open access building (which it should be), free, access to children who are left by their parents without adequate support, and who think that a librarian will be there to pick up the pieces if things go wrong. Oh I wonder what could happen and who could possibly be attracted to that sort of place..... Oh but it has a cafe, so I guess it should be fine then.
Librarians phone the police when kids are crying in the library because their mum has left them and some weirdo or other kid has given them hassle. I was in London so maybe it is not everybody's norm, but it was in that borough, librarians talk to each other and I hear bad things happening in libraries all across the country. Librarians are pretty sick of being treated like babysitters. Expect a phone call and questioning from the police if something happens to YOUR ten year old, because YOU left them alone. Believe me, the police take the same dim view of people who do this as librarians do. You would honestly be better off leaving her at home alone, and you are not allowed to do that are you? So what makes you think that this is any better or more safe, or more fair, or more reasonable? You have a false sense of security that is very misguided and I am honestly shocked, because you don't seem to have a good grasp of your parental responsibilities, and would instead hand them over to someone you don't even know when it isn't even their job. Unbelievable! Look after your own child! It's not the 1950's anymore! Libraries are scary places!