Sometimes we have to accecpt that our kids aren't good at something.
For us it was the realisation that DS has a wooden ear, and with dd it is that she can't spell for tofu. Not even to save her life, and certainly not if she thinks about it.
We have her chanting and writing spellings, but as her teacher has a northern accent and we have PR and I have a slight west country brogue it's not as easy as you might think to get the pronounciation correct.
Spellings are never going to be a strong point, and for some kids maths isn't - it is my belief that we have to accept that some children may never ever be able to spell fluently.
In these days of typing and not relying on vellum and ink, a few misspelt words isn't going to ruin the work. They will never have to scrub at the ink on the page with the grey rubber and/ or have to start over, as it was for us.
If your dd is doing well in all other respects, I would lay off about the spellings, and ask the school to lay off on them also.
Sometimes we need to concentrate on the bigger picture. Having a love of learning, good self esteem and being fluently expressive are far more valuable skills than being a spelling bee.
Tell the school that concentrating on spellings is making your dd miserable and damaging her self esteem, and that you'd like her to accepted for who she is rather than some one size fits all.
In the long term, spellings are not that important as when we wrote in ink with quills on expensive paper. Spell check is your friend, so long as grammar is ok, and similar sounding words with different meanings like there, they're and their are known.
Stop worrying about her spelling - accecpt that it's not her strength, and move along.
Celebrate your DDs positives!