"Is there even a learning disability for slow processing speed?"
OHI?
Have you had a complete hearing exam? Hearing loss in some frequencies but not others can lead to distractibility, low receptive language, and some of the academic struggles you describe. It might not be all of it, but it could explain a good fraction of what you describe.
CAMom suggests apraxia. Has that been ruled out?
As for the IEP, services need to be tied to a diagnosis, and the goals should directly respond to the present levels of performance. OHI might fit for the catch-all issues you have that don't fit under the math SLD. I'm no expert in this area, but learning fast. (We're currently headed down the "looks like ADHD, smells like ADHD, quacks like ADHD, no way is it actually ADHD" path)
You can also think about how you think it might help to her through accommodations. If she doesn't need services, but instead needs more time, type instead of handwrite, a quiet environment for tests, sit near the front of class, or anything else that can change about the structure of how she does the same work as everyone else.
When is your qualification meeting?
She has had hearing exams, albeit it's been awhile. She suffered from frequent ear infections and chronic fluid in the ears from age 3 to 4 until they finally removed her tonsils and adenoids which remedied the problem. I sometimes wonder if the ear infections/fluid played a part in some of her difficulties.
She doesn't have a 504 because the school my girls go to is VERY flexible and accommodating to students and their needs without the need of 504s or even a diagnosis. I know it isn't the legal way of handling things, but we have never had an issue getting accommodations for our dd. So multiple accommodations and interventions have been tried and are not working.
Our qualification meeting is Tuesday.
