If a girl with 20-30 expensive dresses understands that Allah disapproves of wasteful spending and decides to avoid it in the future, what should she do with her dresses, bags, and shoes? Can she keep what she has while not buying new items?
Bismihi ta'āla
Extravagance is haram, and we must not allow ourselves to be dragged into consumerism and purchase expensive dunyawi items that will not hold its value, and are way more that its price value, due to it being a particular brand. Even if you have the money, and you are rich, it still does not justify extravagance. Of course, someones someone might purchase something expensive, for the purpose of investment, as its price will appreciate, and there is nothing wrong with that.
It is good that she has come to this realisation, and be more focused on being moderate and balanced in her spending, even if she has the money. She does not need to get rid of them, if she wants to keep them, but just be more God-wary in the future.
And Allah knows best