12 year-old constantly wants “snacks”

So I have a 12 year old step daughter who will constantly ask me for “snacks” or “can I have a pop tart?” “Can I have some chips?” I could go on. I figured I’d seek some advice. I have been upping her servings at meal times and still, snacks. Even when she doesn’t finish dinner because she’s full, ask for snacks. I’m almost 10 weeks pregnant so this is really putting a dent in both my snacking and wallet. She has healthy options for snacks but would rather eat a whole pack of cookies.