The more I reread your original post, the more I'm like:
"Confront your daughter about the problem?" You're not going to confront her about it, unless you want to ruin your relationship with her. You're going to talk to another adult (because she's your child, not a child, and there is a difference) who doesn't have a lot of life experience about how to wisely spend money. She's not doing anything morally wrong or criminal; she just is inexperienced and needs guidance.
Please don't ask your sister to do it because good grief, that's not her responsibility, and this is still your daughter, not your sister's. You also shouldn't expect your wife to be the sole person to talk to your daughter about important things that come up. You have to figure out how to have an adult relationship with your daughter and not expect your wife to do it for you. Yes she is an adult, but us girls still need our dads, even when we're adults.
First: teach her how to manage money. I was fortunate in that I was a business major and my professors worked in personal finance with their classes. But goodness, high school doesn't teach you necessary things like how to manage money or what a credit score is or pay your taxes. Telling your daughter to manage her money properly without telling her how is like having a teen get in a car and expecting them to know how to drive it on day 1. You need to kindly teach her how to manage her money, just like you taught her how to drive or do everything else in life.
Next: stop giving your daughter money. When I was in college, my parents bought me things that I needed (I had one of their credit cards). Tanks of gas, clothing, school supplies, etc. I never had to ask them for cash. If I made a purchase with their credit card because I didn't have cash on me, I reimbursed them. Now that I'm an adult, I pay for basically all of my expenses, though I still live with them and they don't charge me rent because they know I'm saving money, and it's an arrangement we're comfortable with. So that's the number one thing: if there's something your daughter needs and you're comfortable buying it for her fine. But cash, stop, right now. If she refuses your offer to help her look at her finances, the cash still needs to stop.
Also, you're going to have to respect that you may not always agree with how she spends her money, even after you do teach her how to manage her finances. I manage my money well enough that I'm ready to buy a new car before long; my dad still doesn't agree with all the ways I choose, or choose not, to spend my money. He'll voice his opinion, but once I've made up my mind, he knows that's the end of the discussion. That's very key.