OP, our experience is very different to the facts asserted by mrz.
DD was diagnosed at 7. She was a good reader, but suddenly put in the remedial spelling set. It was as if a weight had been lifted off her shoulders when the psychologist told her she must have been working very hard to be doing as well at school as she had been. From the outside it simply looked as if she were simply more academically average than her friends and sibling. Tests every three years with different psychologists, have produced very consistent results. Her processing speeds are even lower than HG's son (MN stealth boast?!) but this has not prevented her from getting a good crop of A*s at GCSE and a place at medical school.
She wound up at quite a selective/academic school for sixth form, where it was not unknown for Yr 12 pupils to be diagnosed. The extra demands, particularly in humanities, were enough to challenge existing coping skills. I understand the same can happen at University.
Get your daughter tested. Find a Psychologist who will sit down and go through the results with her. The dyslexia probably means that skills in other areas have improved. My daughter has a fantastic aural memory and retains a lot from class, and her visual/facial memory is extraordinary. She is lucky to also be a competent mathematician/scientist.
Then you need to work out how to fill the gaps. So we sent DD on revision courses for her English GCSEs so she could be drilled in exam technique. She knew her stuff but had to be practiced in getting it down on paper. We gave her lots of exposure to French and German (dyslexics can be good at understanding and speaking foreign languages, reading and writing is the problem - so she needed the headroom). She took more than three A levels, as she can normally be guaranteed to misread at least one question, and in the event needed the wiggle room. She revises differently. Succinct revision guides are good, not least because, to GCSE at least, they allow for oral testing.
It was important that her problems were flagged up to teachers. Some had been quite confused by the disparity between her class performance and exam performance. In class tests she was often marked on what she got down and allowed to finish the rest of the test after class. She was often given hand outs at the start of class, or a neat note taker would be encouraged to be a study buddy, so she could photocopy the notes. With slow processing speeds copying from the board is near impossible. She used a lap top up to GCSE, but less so with science A levels. Her A level grades correlate to the amount of reading/writing involved, and probably not to her mastery of each subject. She did try various softwares, but for science, writing was less important. She tends to perform poorly on aptitude tests, which can be as much about speed as aptitude, but makes up for it in interview.
She is taking a gap year, in part because she knows she will have to work very hard at University. She expects new challenges, but at least both she and the University will be able to respond early to any problems.
At 11+ she had a prep school head who did not "believe" in dyslexia, and took her poor CAT results as a sign that she would not be able to cope at an academic London day school, and should head for "country boarding". Our instinct was that she should have the same aspirations as her friendship group, all nice purposeful and fairly academic girls. And individual subject teachers said similar. Luckily her secondary school was very supportive of dyslexia. Thinking differently is a strength as well as a weakness, and there is no reason why she should not make a useful contribution to her University and profession. Not least because she is where she is because she has resilience, flexibility and determination.
Good luck!