I don't entirely agree with the tone of this thread- yes, she's a little girl that loves music, but that's not terribly relevant to whether she's properly learning to read, needs educational input (which you are legally obliged to be offered, unless you have withdrawn her from education which I don't think you have, so some worksheets are not adequate at all) and keeping her up to speed with not just reading and writing but also maths,
It's a bit irrelevant that in some Scandinavian countries they don't start the formal part of their education til 6/7, because this child is 6 and would be starting that fairly soon, and by waiting til 7, they are then expected to progress pretty quickly to learning to read, or maths ability, they don't go as slow as in the UK!
I would repost this in the Special Needs section and see how you can get your local authority to step up and provide more educational support- you've done a great job but you shouldn't be on your own in this, you need specialist imput/tutors/far more support than you have been getting, I feel like your dd is falling through the cracks as she's not out of school for a day or two, but months on end. She'll also need support for maths as she goes forward if she's missed a lot.
Some great suggestions on here in terms of supporting literacy, reading a lot, getting her to read things she likes the look of, audio books, but ultimately she does need to learn to read. My dd was six and also couldn't read (unlike my other one who read aged 4) and we did an intensive six months of 10 minutes of her reading a day, with set schemes, and she cracked it. She is dyslexic and it was a massive struggle, but the answer isn't just hope it all happens later on and delight in her musical talent (!) I know you didn't say that but some of the posts on this are a bit over-romanticized about what it's like to get children who are outside the school system a lot to be on a par with her peers.
She isn't going to get why literacy or maths is so important right now and may not want to do it. No need to panic, every opportunity for her to get this in the coming couple of years, but I really think there's a statutory duty to educational provision which is being failed here.