Diagnostic testing for differences

I teach in a two year college nursing program. Our students are required to take a math test (basic calculations of medications) in order to progress through the program. I have one student who told me that she can not understand the math. When looking at her high school transcript, she had a terrible time in basic math courses. Unfortunately, she was placed in college algebra(incorrectly) upon admission to the college. Her testing scores (if used appropriately) would have indicated placement in the beginning algebra (elementary math). Now she has struggled to do the math calculations. Where can an adult go for diagnostic assessment? The other instructors feel that she may require longer for testing but we must have documented information stating that she has a learning difference.