It is considered. While it does not count towards the $4050 gross income test (being nontaxable if its her only income), it is counted towards the support test.
Since the child is not your child, you must provide more than half of her support. You need to determine her entire cost of living for the whole year (food, housing, medical, education, clothing, travel)- did you provide more than half of that support?
When a child has income such as Social Security Disability, sometimes that supplemental income is supporting them more than any person is, financially-speaking.
Also, did she live with you all year and does she have parents in her life (that would claim her)?
(You don't have to answer the latter part.. its just what one would think of, as you didn't indicate that you were raising this child)
Try this tool out:
https://apps.irs.gov/app/IPAR/investigate/IPAR_1/en-US/Attribute~Dependents~global~global/qs%24s1%40...
