Obviously it depends on your income, your financial goals, any debts you have--first. Second, I'd consider how important it is. Is she professionally going to be involved in music someday or is the potential there? Then there might be more cause to spend more than normal. But never put yourself in debt for this stuff - and that includes 401k deficit. These are extras and retirement, housing, food, bills, existing debt all need to come first. Even put saving for her college tuition on that list if you plan to help. If there is money left over and you are fine giving up the fancy vacations or fancy car for it, then go for it! Just my two cents.
