I am an English tutor and teach kids of all different ages and abilities. One of my students is only 7 years old with suspected dyslexia and she is able to write much better than this.
It also leads me to think Sienna's newest instagram post of her reading a novel book is completely staged, if she's unable to group together words and sentences I highly doubt she's able to read a book like that unaided. This age is crucial in developing reading, writing and spelling skills and if it's missed now she's going to really struggle in the future. It's so cruel. Like all kids, even those with dyslexia or other learning difficulties, with the right education, attention and learning tailored to their needs, standards can be met. Her parents should be reading with her every night, not novel books if it's beyond her writing levels, but books suited to her needs, they should be helping her to correct her mistakes, showing her how to write neatly within lines, have gaps between words. I'm in awe of the negligence here. You don't need a degree in teaching to help your child read and write.