She also has a bad memory and is slow at stuff. Her concentration isn't great I can ask her to do a simple task and she will mess around. By time time she gets round to doing it she will have forgotten what I asked her to do.
That sounds like my son. His dyslexia tests came back showing that one of his weakest areas is what's called "working memory" (I always think of it by analogy with the on-chip memory in a computer - the bit that holds the information you're working on right at this moment) and processing speed. It was particularly noticeable when he first started trying to learn to read - given a three or four syllable word, by the time he'd managed to decode the last syllable, he'd have forgotten what the first one was!
He also struggles with distraction (where he's seated in class makes a huge difference to this - if he can effectively be given his own little corner away from other people, he loves it).
I think some of the messing around can come from a feeling of "well, everyone's treating me like the class clown, so I might as well live down to their expectations."
As a PP suggested, I had to have a private assessment (a lot of education authorities don't do them any more - ed psych funding has been cut back to the bare bones, so they spend most of their time fire-fighting with the children with the most immediate and disruptive special needs, and don't have time for the ones who are quietly sinking.) I realise this is a counsel of perfection, and it just may not be possible to do this given your situation, but if you can't afford it now, maybe start trying to put away a bit of money once you are working, just a little at a time, with a view to having her tested before she has to start secondary.
www.bdadyslexia.org.uk/parent
and
www.nessy.com/uk/parents/dyslexia-information/
are a couple of sites which can help with strategies - basically a decent teacher should be putting these in place anyway.
One thing that really struck me when I first started finding out about dyslexia was that there's so much more to it that simply poor spelling/reading and mirror-flipped letters (which my DS doesn't do).
Here's an article on processing speed:
www.dyslexicadvantage.org/understanding-processing-speed-and-dyslexia/
and one on working memory:
www.psychologytoday.com/gb/blog/keep-it-in-mind/201601/dyslexia-and-working-memory
For the poor working memory, one strategy that would help if you can get the teacher to put it in place is to break down tasks into bullet points and get the teaching assistant to check periodically where she is with the tasks, that she's doing them in the right order and hasn't missed any out.