Since you already know that you and your mother have differing opinions of thrift store clothing, I have to wonder why you would even bother informing your mother of your purchases.
Do you have nothing else to talk about except clothing? Must it truly be all about you all the time? Or is it that you just enjoy the drama and the attention your obsessive behavior creates?
~ Your mother is entitled to her opinion of thrift stores and their clothing selections. It is her right to express her desire NOT to wear such items.
~ You are entitled to shop at thrift stores and to wear whatever you choose to purchase, whether it has already been worn, or not.
~ You have the right to disagree with each other. But for you to call your mother a bitch and an S.O.B. simply because she does not share your love of thrift store clothing is rude, nasty, inappropriate and abusive.
If you cannot allow your mother (or anyone else) to have an opinion of thrift store clothing which varies from your own without either obsessing over whether your purchases are acceptable or flying into a rage, then you have a larger problem than a fight with your mother.
You need help. You need the kind of help that can only come from intensive therapy with a qualified mental health professional.
Please do your mother a favor. Stop spending your unemployment benefits on thrift store clothing and start spending them on finding another place to live.
Then, you can do what you want and you'll both be happy. You can shop to your heart's content and buy as many used clothes as your budget allows and your mother won't have to worry about doing or saying the wrong thing all the time.
P.S. You have already said that your mother is in her 80's and drives her own car. Yet you are now saying you had to pick her up from school? What's wrong with this picture?