From what I have learned listening to psychologists describe the RIAS and the What's Missing subtest in particular is that it is a non-verbal measure that is similar to the Picture Completion of the WISC that measures alertness to details and visual discrimination. Generally, more than a 15 point difference between any scores is considered significantly significant and an indicator of a relative strength or weakness. That said, it is not that unusual to have some variations in scores between tests.
If you want to get more information in the visual integration/ visual perception realm, at some point you could have her evaluated using other cognitive tests such as the WISC IV, ROCF test and others.
These scores alone do not point to a problem by any means. And, you have no idea if this score is even an accurate measure of her skills in this specific area. What you have is a score that reflects how she did on the test at a point in time.
If she does not have any problems - and it doesn't sound like she does - I might just put it in the back of your mind, and support her as she enters into the gifted program. If she is "just" high-achiever bright and happy, this would not be a bad thing.
