Sounds like you're on to something! I very often hear from parents who are not as insightful, and who are focusing on ways to treat the symptoms but not get at the underlying problem! Your daughter may indeed be showing early signs of learning disablilities, and waiting to take a closer look at why she is struggling will only make her feel worse about herself and prolong the frustration she is feeling (and you and her teachers are experiencing in not knowing how to help her get back on track).

Some pre-referral (for formal evaluation) activities should be undertaken. Gather information from all of her teachers about whether (and how) she is struggling in different areas of learning - is she experiencing the same frustrations in reading, say, that she is in math? (and not just in terms of how well she does on standardized assessments). Also gather information about what specific efforts have been made to address her learning delays -if she has not learned to read, it could be that she has not been TAUGHT to read. Some short-term, very targeted, intensive instruction could help answer this question and uncover whether there are some important, foundational skills she has not yet learned that re causing her to guess at words rather than decode them. And it sounds like there are no concerns about her oveall cognitive skills and that intelligence is not a factor that could explain her struggle with learning.  

Once you (and your daughters teachers) have become "experts" and can reflect upon what has been tried, for how long, what has worked or what has not resulted in success, you can (and should) request (in writing) that a formal evaluation be done, with the purpose of filling in the gaps and discovering what tools and strategies should be employed to make learning fun and allow her to catch up to  her peers.

Look at NCLD's LD Checklist (http://www.ncld.org/en/publications-a-more/checklists-worksheets-a-forms/ld-checklist-of-signs-and-symptoms) for a quick overview of chaarcteristics ranging from the early years through adulthood.