There'll be a lot of preparing for engagements and events - everyone who meets her mentions how much she already knew about their project, organisation etc and how interested she was and asked all the right questions - that can take quite a bit of work, it comes easily to some people but it's just like preparing to make a presentation or big meeting at work for the rest of us - you can spend 2-3 hours or so prep for every actual hour of doing the thing. (and yes - she will have staff to help brief her but she's got to put in the hours reading it, memorising it, rehearsing speeches, learning people's names and titles) Reading the newspapers and listening to the news will also be part of the 'job' - to be confident moving between different social situations.
Then while it's definitely nice to not have to do the grunt work of cleaning, grocery shopping, laundry etc - there's a certain amount of time needed to plan and supervise employees - just like any management position in an office.
And then there's the time it takes to meet all the expectations for the society rules for that kind of role - lots of letter writing, diary organising etc, hosting, going to dinner parties with people you don't know or have no interest in.
I'm pretty sure she has a very full schedule - it might not seem like work to some people but anything becomes 'the job' when it's something you have to do every day because it's your role.
There's not much flexibility over the yearly schedule either.
This is a role where she knows exactly where she has to be every Easter, Remembrance Day, Monarch's official birthday, Commonwealth Day, Christmas for the next 60 years - or until she's dead (or there's a revolution and we institute a Republic - in which case I bet she'd heave a sigh of relief and then definitely spend her days playing tennis, lunching and having spa treatments)