@cheeseismydownfall
I'm sorry to hear that, OP. I think all teenagers find something to blame their parents for. We are fortunate to have been able to to travel a lot with our children, but all that is forgotten in their never ending pleading for a dog. The eldest in particular is insistent that absolutely all of his friends have dogs, and simply won't hear the reasons why it isn't at all practical for our family.
^ I think this is very true. Teens are almost programmed to be dissatisfied with the status quo and "want more" and feel restless. It's part of growing up. And it's this urge that makes them leave home and explore the wider world. If it wasn't travelling, it would be something else. In particular, teens tend to want the opposite of what their parents want or can provide.
Sometimes teens can't quite articulate why they feel the way they do, so all of their feelings get centred on to a new phone or a holiday. In this instance it's helpful to address the feelings behind the request rather than the factual request itself. So talk about and acknowledge your teen's feelings of restlessness and need for increased independence. Is there any way you could meet her needs in a different way such as buying her a bike, helping her to get a paper round, go hacking on horseback (these things are very difficult ATM I realise).
Also, our society almost programmes us adults, never mind teens, in to thinking "I'll feel better when I have saved up for this car/renovated this house/gone on holiday/lost two stone" so it's helpful for teens (and ourselves) to learn how to feel happy and ok in the present moment eg mindfulness. People think it's a bit hippy but it really isn't; it helps us to banish depression about the past and anxiety about the future. A gratitude journal can help with this and has been shown to change the neural structures in the brain.
Good luck op. And don't fall in to the trap of letting your teen make you feel guilty. It can be very wearying and upsetting to have your own child criticize you and, in a sense, be told that, in their eyes, you are not doing a good enough job, when for all of their childhood, you have put them first. Keep calm, be sympathetic, tell your DD you love her often (as all teens assume everyone is working against them somehow!) but don't be drawn in to her cry of "all my friends have more/better/easier". Be strong, quietly confident and sympathetic, but stick to your guns. They need you to hold the boundaries for them.