Does she have a credit card with decent (or non-existent) foreign-usage fees? If so, she won't need to use all that much cash. In general, I'd be in favor of making fewer and larger withdrawals in your daughter's situation, but pickpocketing is a growth industry in quite a few European tourist hotspots, Barcelona being one of the worst. She'd be well-advised to make the withdrawal and go straight back to her room/apartment to leave the excess in a safe place. I lock my excess cash and back-up credit cards in my suitcase when I'm out of my hotel room.
One thing to consider is that some ATMs dispense rather large currency notes when you make a substantial withdrawal. I don't like having just a 50-euro note, because some small shopkeepers will not have or want to give up the change necessary to break a bill of that size. My usual withdrawal is 40 euros; but I have a no-fee ATM card.