Her social security payments are not taxable because she did not earn enough money to make them taxable.
She does not have to file a tax return because her earned income plus one half of her social security benefits is less than $25,000. This assumes that your daughter is single - the base amount is different if filing a joint tax return.
To find our whether if a child's benefits may be taxable, compare the base amount for the child’s filing status with the total of:
One-half of the child's benefits; plus
All of the child's other income, including tax-exempt interest.
She may want to file a tax return if she had federal income taxes withheld from her paycheck. She would be entitled to have those taxes refunded to her. State tax law may be different so you should consider if she has to file a state tax return.
See IRS Publication 915 for more information.
https://www.irs.gov/pub/irs-pdf/p915.pdf