To answer your question in the Title:
Depending on how old it is, how often the previous owner used it, and how much stuff they put into the bag, I could see it as normal wear and tear.
Chloe uses excellent leather but their leather can be quite soft. I don't know what kind of leathers that Marcie's are made in but from my experience, Chloe leathers can be quite buttery and soft but also means more easily to wear down.
Another thing is that sometimes the Chloe hardware can be on the bulky or heavy end depending on the design, which could also increase wear with use and additional weight.
I had a beautiful goatskin Chloe bag years ago, the leather was soft and beautiful and it had a very heavy metal clasp in front. I personally don't think I put a lot of things in my bags (6 ring key holder, small wallet or card holder, phone), but I soon saw the metal clasp pulling at the leather over time and I quickly sold it.
Btw I noticed you also said vintage, which I am assuming is about 10 years old? Then if it has been used for 10 years I'm pretty sure that wear and tear comes with all those years of use.
Regarding repairs:
You could try to bring the bag into a store and see if they can replace the leather. It may be possible since this bag is still in production. But it will probably come with repair costs.