Help: What is the normal tax rate withheld from paycheck as F1 student on CPT

I have a friend who might be overly taxed on federal withholding. She is currently on CPT and the total taxes withheld is 31.2% of every paycheck… Is this normal? Should it be lower or is that the standard for F-1 students on CPT/OPT? She doesn’t have any other deductions besides federal and state withholding on her pay stub.