I know what you are going through OP, my weekend used to be exactly the same. However, in the last few weeks I took control and things are starting to change, but I had to start to give her responsibility (Yr2) and take a step back.
After a big meltdown three weeks ago, I very calmly said 'fine, if that is your decision, I will write a note to Miss and explain that you didn't want to do it....'. Note was written and I had a quick word with teacher. Next week, when I suggested the note she reluctantly sat down and did work, which usually takes all of 15/20 mins - and she can do it easily, so not sure why the fuss!
Last week, I asked her when she would do her homework and she told me, at said time she said she didn't want to, I again said 'fine, I will let Miss know' and she paniced, 'no I will do it, please let me do it', we had a bit of messing, but not much, however, because I have also been reading a book about 'How to talk to children....', I didn't give one negative....I usually suggest she writes tidier, stops figiting, takes a bit more pride etc. etc., but instead tried to see the good bit ('you underlined that well')!!! It was all a lot stressful after all it is not my responsbility that she keeps her work neat - I had to let that feeling go!
This Saturday, I suggested we do some of the homework before we went out and she said no and we had a bit of negotiating, before we decided on Sunday morning and I told her I would be able to help her then, but not later, because I had ironing etc. etc. to do and we would like to go out somewhere too.
This morning, I reminded her about her homework and she had a little rant.... I said... I will be here for another five minutes, then you will have to do it on your own, she came straight away and sat like a model child and did all said homework! I didn't do anything, sat next to her with a coffee so was able to help if she asked, but did get up a few times and do other stuff, giving the impression I was still there.
What was great this morning, is that I didn't have to find things to be positive about - she started off with the neatest writing I have ever seen her do, she wrote joined up the whole thing (this is a big deal for dd), and at the end of it, we were both flying high on our success. I still can't quite believe it!
I know this isn't going to make you feel any better right now, but I wanted you to know you can turn it around in a very short time. I just hope it continues. The hardest point, was just letting go.