Welcome! You've come to the right place! Lots of people here have been right where you are now and are full of knowledge and help.
First, what your testing is saying is that with 90% confidence they can say that your daughter's scores on this test (the RIAS, which is a good test) are at or higher than 99.98 percent of the population. That's really high! It is very unlikely that she is not, at the very least, highly gifted. These scores would suggest that she is in what some would call the exceptionally to profoundly gifted range. These terms are somewhat ambiguous, though, and the way in which they are used is inconsistent. Sometimes IQ tests of the very young (less than 6) can be a bit unstable, but the score is not going to drop 3 standard deviations (45 points)to make her "average." Your daughter is what we like to call around here wicked-smart. Are her scores matching what you're seeing at home? Keep in mind, too, that your lens might be slightly skewed so you may not know what "normal" is!
Whether you tell your daughter what her scores are is a tough question. We've had discussions about this in the past, I know, so you will want to search for that discussion on this site.
Now, keep in mind that she's still the same girl you've known and loved and parented her whole life and you've been doing just fine so far, so try to feel confident that you can handle this. Besides, you're likely quite smart yourself and have an inkling of what a smart kid likes and needs to be happy. It's easy to get freaked out reading about giftedness and what that can mean as a child grows, but you can really only focus on the short-term and cross any other bridges when you come to them.
What is your daughter's educational situation right now and how is it working for her? If it is good right now, yay! Stick with what works unless it doesn't anymore. If, at some point, it's not working, you have lots of options from enrichment to subject acceleration (e.g., going up a grade or two for math) to grade acceleration to homeschooling. There is no one way that works for everyone. So much depends on ability and personality and peer groups. We have people here whose kids go to the public school, to private schools, to gifted schools, to boarding schools, and homeschool. Some of us have combinations of all these options. But try not to be overwhelmed by your options. Take your time and read and ask questions here.
Anyway, welcome again, and feel free to search discussions and ask as many questions as you have as they come up!
