DD stills mixes her letters up ie she will spell "cold" as "clod".
This would tell me that she isn't breaking words into their individual sounds as she spells but is trying to remember the letter 'string' which makes up the word. If you encourage her to break words into their component 'sounds' and spell each sound in the order in which it comes in the word, then, sound out the word to check she has it right, she may find it easier. I do think that mistakes often arise because the child has never been shown the logic behind spelling. Even schools which seem to teach good phonics for reading don't always seem to apply the same approach to spelling.
Programmes like Apples & Pears are a great help.
This is part of a post I wrote on another forum. I don't know if it helps:
I am always slightly surprised that poor spelling is regarded as a key indicator of dyslexia and that children may even be categorised as 'dyslexic' on the basis of poor spelling alone (as in, how many times have you heard parents say that their child is dyslexic; they can read fine but their spelling is poor?). I know that spelling is constantly characterised as the reverse of reading and indeed it is, insofar as reading requires the conversion of symbol to sound whereas spelling requires the conversion of sound to symbol. But I think this is a very simplistic view when it comes to English spelling. I think that poor spelling in English is less an indication of a cognitive deficit (or 'difference') and more a fairly normal condition for a very large proportion of English speakers!
We know that learning to read English is more complex than many other languages but one of the key differences between learning to read and learning to spell is that in reading we always have a visual clue in front of us. Once we have mastered to automaticity the 1) conversion of symbols to all the sounds those symbol might represent, 2) the art of trying each known sound/symbol correspondence if the word is unfamiliar and how to find the correct pronunciation if need be 3) the embedding of the word, through practice, in long term memory for reading 'at sight' and 4) the association of meaning with the word, the job is done. And there are only some 168 -180 common correspondences to learn, plus some more rare ones which we learn over time and with reading experience. But probably not more than about 400 bits of information to learn?
Whereas spelling involves deciding which alternative sound spelling is to be used in specific words without any visual cue (unless the speller is one of these people who claim they can 'see' words as they spell). There are some 300 homphones alone in English which have to mastered in addition to the 100s (if not 1,000s) of words which need a decision on just which sound spelling has to be used in them. So, a far greater cognitive task than just saying a sound in response to a symbol when reading. Added to this is the complication of kinaesthetic memory. Every word has a unique 'feel' to it when it is written (whether by hand or typed). Skilled spellers don't consciously think about the individual letters in each word they write; if it is a familiar word to them they just 'think' the word and the hand & brain respond with the spelling. So a child who has habitually spelled a word wrongly for a number of years is going to find it hard to break the kinaesthic memory, especially when thinking about other things, such as the ideas they are trying to express in writing. 'Reprogramming' the hand & brain takes time and a great deal of practice (our 1950s teachers were absolutely right to make us write out corrected spellings at least ten times!)
I can also never understand why phonetic spelling is regarded as 'deviant'. That's how our literate forebears did it for 100s of years until it was decided that spelling had to be 'correct' to be acceptable.