My daughter will be 7 next week and she often writes letters and words the wrong way around. She is right handed. She is a good reader. My younger daughter, age 5, has been much quicker to learn to read amd write, and rarely writes letters the wrong way around. She has also been quicker to learn to dress herself, fasten buttons, etc. Could she be dyslexic?
Looking at your 'profile' I see you are a TA, so I guess you are used to some children doing that when they first learn to write. Usually, of course, it is b,d,p,q, 6, 9 as they are all 'a circle and a stick' to some extent.
If it extends to other letters it could be more of a problem. I have my own theory that children see letters just as shapes, until they are more experienced, and as with a circle or a square, its position and orientation makes no difference to its shape. I speculate that letters may be the same for some children. I was a TA / helper for twenty years; for letters b, d, p, and q I used to tell Yr 2 the correct terminology of 'ascenders and descenders' for the 'stick', and they enjoyed that because I said some adults didn't know it!
Incidentally, many of the technical terms used in computing regarding fonts, text spacing, and other aspects of text, come from the hundreds-of-years-old traditions of type setting, and it has an interesting history.
Regarding dyslexia, I'm not qualified to comment; it is a shame though that so many parents, even trained and knowledgeable ones such as yourself, fear 'the worst' as soon as their child isn't matching the performance of their peers.
Oh and I don't 'fear the worst' as you say, I just wonder if she might be dyslexic and might need some support. I don't think of dyslexia as a 'bad thing' just something different. She has just done SATs and found them very upsetting, unlike the rest of her class. I would like to make her school life happier for her, since she is so little and shouldn't need to feel so stressed at school.