Letter-Word ID is not a measure of phonological processing, but of word calling. It's not even a good measure of decoding skills, as it's a list of real words that she may have memorized. If you want PP testing done, the gold standard is the CTOPP-2. There will be a decent (at face value; no clinical track record, so I can't speak to that) PP section on the new WJIV. The existing WJIII has a couple of PP subtests on it, but they are all in the extended set, not the standard. One caveat: very bright, verbal, adolescent dyslexics may do fine on the majority of the CTOPP or other PP measures, as they often have developed their own compensatory mechanisms. Even if there are phonological processing issues, they tend to be very subtle by this age, and with this cognitive ability level. You'll have to pay careful attention to the phoneme manipulation tasks (e.g., deletion, reversal), especially those using non-real words, where she is less likely to be using general verbal knowledge and cognition to compensate for weak PP.
The top line here is actually that the numbers you report would qualify her for an IEP, not just a 504, as the writing achievement is well below both normative and individual expectations. You are also reporting educational impact, despite her good grades, as she is having to use inordinate amounts of time and effort to complete grade-level work. She would qualify under pretty much any of the current criteria for SLD: aptitude-achievement, pattern of strengths and weaknesses, cross-battery, and RTI (if you use her reading/writing speed). The very low TOWL scores indicate that it's not just an issue of writing speed, as the majority of the TOWL has no time limits.
You must be very proud of her maturity, poise, and self-awareness. That is what will take her the furthest in life, and as a human being, without a doubt.
