Lori
You sound like a caring teacher. To help this child get the cooperation of the parents and then paper her bedroom with pictures and words to help build her vocabulary. She will need to watch English videos, as many as she can for her age group, things like Lion King. Maybe she can do this in school too.
If the parents can afford it she can go to an enrichment play group after school or on the weekend. In Korea and Japan these after-school classes (hogwan schools) are standard practice, piano, computer, math, Taikwondo, English, Chinese writing. The children can absorb it all when they are young. If the parents can't afford it then they can start a small home group themselves and share the effort with other parents.