Hi life, it sounds like a bag of clanky arse, imo. 
Have I got this right? You've had a recent annual review and want changes to the statement - and as things stand now, the school aren't implementing the statement in its current form?
One sub-level progress in 5 terms is not good progress at all - and it's certainly not 'adequate' progress. If you're still on the statementing track, 'adequate' is the word that matters here, as that's what the law recognises.
English education is moving gingerly away from NC level- & sub-level-based assessment, but many schools are still using this approach. Not sure what age your DD is, but to give you some idea of the rate of expected progress: children are expected to make at least two full NC levels of progress between the end of Year 2 and the end of Year 6. That's 6 sub-levels of progress, to be made in 12 terms - so roughly 1.5 sub-levels per year.
So for 5 terms, you'd expect an average child to make about 2.5 sub-levels of progress. Not one. You need to ask them why they consider 1 sub-level to be good progress, and if necessary get them to spell out in the statement what 1 sub-level of progress actually means - that even with current provision, DD is still falling behind.
The other thing to bear in mind is this - how confident are you that she's even made 1 sub-level of progress? Internal primary school NC assessments are notorious for being total bollocks subject to inflation, and I'd imagine that the pressure to inflate grades is even more acute now that teachers are having to deal with performance-related pay - their own pay rises depend on being able to show progress.
I'm not too sure what's going on with the parental views. Have the LA badly summarised your views in the main body of the statement? Have they deleted your views from the statement's appendices that contain the evidence? Alternatively, has the school failed to include your views in the annual review report that they sent to the LA after the annual review meeting? In most cases, they are on dicey ground if they have failed to represent your views properly. You shouldn't have too many problems getting this sorted.
Best of luck with Thursday's meeting. Do you have any backup? If your LA has half a brain, they'll be leaning on the school to implement the terms of the current statement - it's the LA that's legally responsible for making sure the provision is delivered, not the school.