Caveat first: while SBAC scores are nominally on a continuous vertical scale across grades, since not all grades see the same item difficulty, the highest and lowest scores obtainable in a grade (your DC's scores would fall in the former category) are less reliable than those in the middle, and may be either over or underestimates of true academic achievement. They are subject to many of the same interpretive caveats as grade equivalent scores, since they are samples of skills, rather than comprehensive surveys of all grade-level instructional requirements.
That being said, if these were true scores, they would put her performance in the advanced (level 4) classification for fifth grade (at, presumably, third grade), comparable to proficiency (level 3) in the literacy score for 11th graders, and math score for 8th graders. Of course, as SBAC only allows items up through grade 4 on the grade 3 test, these levels are clearly rough estimates at best, and cannot be considered true scores.
If you can find data on your district's performance (levels 1-4), and the percent of students who typically score at each level, you might have additional supporting evidence. This data is generally available on the state DOE site, listed by school district.
Advocacy may also be more effective if you can demonstrate that your DC performed at these levels uniformly, across all of the skill areas encompassed by the broad literacy (4 areas) and mathematics (3 areas) scores.
https://www.smarterbalanced.org/wp-content/uploads/2015/08/2014-15_Technical_Report.pdf
