My oldest son chewed his sleeve at that age - self soothing mechanism. Don’t call too much attention to the behavior. Simply redirect - coloring, beading, braiding, etc. keep hands “busy. ” She can help fold towels at home. At school maybe teacher can let her stack glue sticks at her desk (it was his favorite)at times of self soothing. Check to make sure teeth aren’t bothering her but it sounds like a typical kid behavior. Adults chew pencils, pen caps, etc.