Accidentally received Stimulus Check

My 19 year old daughter received the stimulus check despite being claimed as a dependent by my husband and I. We suspect it may be because of a mistake made on her own tax return last year, but we cannot find her tax return from last year in order to see what went wrong. We sent for copies of them, but haven't received copies yet, so we can't be sure what the mistake was that caused her to receive stimulus money. Is the money spendable? Will the IRS want to collect this money once they realize a mistake has been made?