Hi OP, we were in the same situation as you a few months ago. DS (9) started tutoring for the 11+ and had a similar amount of homework to your DD. It was hard going and a steep learning curve for all of us for a few weeks. In my experience the majority of the work is done at home to reinforce what they learn during the session. My DS was really slow and complained a lot about the homework at the beginning too, but he's got used to the format of the work and is much quicker and complains a lot less now. We also had to literally stand over him at the beginning to make sure he did his work.
He still has the odd moan but the way I see it, half an hour three or four days a week of tutoring homework is a lot more beneficial than the tv or PlayStation. He gets rewards for effort (big days out, more so than we would do ordinarily, things like that) which he loves, but he knows that we expect him to work hard for those rewards.
He doesn't like sitting alone to do his work so I usually potter around upstairs so he knows I'm there.
I would suggest giving your DD as much support as she needs during the first few weeks (I think it took us around 4 weeks before we noticed DS getting quicker at his work) and gradually withdrawing your help.
I still have to manage DS' work i.e. tell him which piece of work to do each day and I always look through it first so that I can help him work things out if he's stuck without actually giving him the answers if you see what I mean.
The tutoring is a big commitment from all sides and if I were you I'd give it a few more weeks before making a decision about whether to stop.
I'm so glad we persevered with DS. I'm really not sure whether he'll pass - he's a bright kid and he's certainly got the potential but you just never know. The way I see it, knowledge is something that no one can take away from him and I can see how the extra work is helping him generally.
People have very strong opinions about 11+ tutoring but each to their own. I would really struggle to know what resources I needed to help DS prep for the 11+. The tutoring takes care of all of that but there is still a massive commitment from the parents to manage the homework.
Sorry - it's turned into a bit of an essay! x