Well I knew at year 3 but my son's help only kicked in at year 9! He left Primary with an age 6 "ability" in English.
Try and find out what helps her as there are so many different forms of dyslexia. My son, as an example, sees every letter twice and they move - but not in unison. Small typeface can look to him like a jumpy qwerty code. We didnt understand this until year 9. No wonder he struggled to read and write whilst being really clever!
We only discovered this after years of trying different strategies.
We then had a colorimetry assessment done and he had prescribed coloured glasses....in rose! Lovely for a teen boy! That helped control the text better and bring the duplicated letters closer together. Not perfect but much much better.
For reading he read ability appropriate stuff (when he had to) but he listened to age appropriate audio books from the charity Listening Books. This kept his comprehension and vocabulary at an age appropriate level - even if he could write that down. We didnt read at home apart from school homework - he listened to audio books all the time. I'd recommend looking into these for her. Listening Books is a fabulous charity.
He was an excellent musician...so we really encouraged that because it gave him confidence and being "best at something" also built his self esteem when he spent most of the school day frustrated. He joined a youth theatre which help distract his mind from the frustrations of the school day.
He managed to drag himself through GCSEs with adjustments and his glasses which he had in year 9. Gained amazing C grades in most subjects and the odd B and the odd E.
Then he followed his passion...computers and coding at BTEC...nailed a degree apprenticeship....and has just bought his first home at 27!
So, don't worry, alongside helping her read and write, ensure you keep her self esteem high. Let her do things she will, inevitably, be amazing at.
Good luck! And stay strong, little one. You are AMAZING.