I would second what has already been said, but also advise you to discuss the situation with her tutor - or indeed tutors, if she is attending a number of classes.
If she hasn't been completing the homework, I would have assumed the tutor would have contacted you by now to discuss this issue, as this is presumably a crucial part of the tuition; if not completed, surely she must be struggling in class?
I'm also aware of some tutors giving two-inch thick piles of papers to children every single week, to complete, not all of it relevant. Few children can keep that up for any length of time. They are only 9 or 10 years old - they're still young. If this is the case, it may be time to work smarter, not harder.
The 11 Plus is a difficult process. If you're one of the 'lucky' ones at the end it is a process that is well worth going through. The majority of those who enter it will not gain an 11 Plus place. The posts above have mentioned the need to carefully weigh up a child's chances, based on their motivation and work ethic as well as their ability.
I have seen parents whose children either do not have the capacity or the industry to reach the level required, shell out huge sums of money and go through months and months of misery - only to have their hopes dashed in the end - after spending a year telling the child how terrible their local school is.
I know of children who are still upset years later at their 'failure', having been assured all the way by optimistic parents and tutors that they were definitely going to make it. Because of this, I actually have a great respect for parents who decide that the 11 Plus is not in their child's best interests, and don't pursue the rocky route to Grammar.
However, don't misunderstand me - I personally see Grammar Schools as offering truly brilliant provision for those children suited to them - and they are well worth working for. I have been through the process twice as a parent - happily successfully, and I am currently on my third child, in Year 5.
For each child, the 11 Plus had a pretty significant impact on us all, and each child, in turn, in a family of 5, had the lion's share of my attention during those final 8 months. There were times when they didn't want to complete homework, and it usually took/takes assurance and bribery to keep them on track. I don't think there's any child in the KE Grammar Schools who didn't work for their place. Many, if not most, will have had significant amounts of tuition and home support. However, your child herself does need to want to do it. For all their occasional intransigence, my children were 100% sure they wanted to go to a Grammar School. They did not waver in that once - although they liked different Grammars depending on their open day experiences! Without this motivation on their part, I admit I just could not have seen the process through, as I needed them 'on side' with our program to make their aim happen.
Your query is a good one as I believe it is one that a great many parents do have.
You will first need to assess not just the 'chances' of a place, but whether your child will thrive in the highly competitive, academic environment of a Grammar school. You also need to find out how your daughter really feels about her school choices, too - this isn't always easy to gauge - as we all know, some children are more complicated than others! Your child's teacher will be a good starting point for a conversation, but the tutor(s), with closer experience of the actual 11 Plus requirements, should be even more lucid and helpful in their feedback.
I should also note that every year, some very bright and capable children do not attain an Grammar School place due to 'burnout'. They are driven for many months on a schedule that most adults couldn't keep up, and with levels of pressure that most adults couldn't take, and this tends to lead ultimately to poor scores at the end. Each of us have to allow our children adequate rest, relaxation and fun, too.