I can relate to this, my DSD was similar at 14-15-16 (but she was at home ALL the time!). There were a few things that worked very well for us...
If your DSD's birthday is coming up, maybe you could use that as an opportunity for a conversation about increased responsibility and maturity. Does she get pocket money from DH?
One thing that worked for us was we increased DSD's pocket money, and also gave her assigned chores. Half the pocket money was "automatic", and the other half was linked to doing her chores properly and without excessive prompting or complaining. She then became responsible for paying for her own 'non-essential' items. So we would have bought the outfits for work experience, but not make-up, clothes she didn't truly need, cinema tickets, and so on. Before this, DH would basically have bought her anything she wanted and she had a very entitled and wasteful attitude.
She should have chores at your house. If she is there three evenings, get her to cook and wash up for one meal - start with something simple and move on - if it is totally foreign to her, then you or DH can do it with her the first few times, but maybe fix upon a dish which will be her 'specialty' and she can fix every weekend. Maybe one other chore over the course of the weekend - hoovering, perhaps?
When you did up her room for her, did you include a laundry basket and a bin? Does she use them? Do you do her laundry or does it go back with her?
At 15, too, she can be responsible for her own breakfasts and lunches. Talk to her about what she'd like you to have in - I get the DSC the cereal they prefer and reasonably healthy lunch and snack food, and they sort themselves out; I might do brunch on a Sunday if everyone is around, but I do it when I feel like it, not as an expectation.
And yes! Stop running in with nibbles and so on. Start asking her to go fetch things for you guys, or to put a pot of tea on, once in a while.