Would it bother you if your mum buys the same clothes as you?

So I bought some Dr martens and she went and bought some.
I was going to buy some filas, so because she needed new trainers I said she could buy them instead.
I bought some new balance trainers and she said she liked them. I went with her to buy some of the modern styled ones (that are different to mine) and she couldn't make up her mind. In the end she didn't buy them.

I bought some addidas trainers and she tried them too and said they weren't comfy.
But last Saturday she went out and bought the same ones in the green.

I'm pissed not because we have the same things but because she gets annoyed that her sister someone she sees maybe 2 x a year copies her clothes.
She makes such a fuss that she goes out her way not to wear anything new if she sees her so she can't copy it.

We had a little argument about it. Because she couldn't see the issue.
And now she's being petty by saying she's going to sell them on vinted even though I told her I didn't like that she had bought them last Weekend before she walked them out on the high street.

As I was going to buy them in the green also!

Am I being petty?