AITA to keep the suit I tailored to me from sister's clothes she gave away?

My sister gave me a bag of clothes she used to wear to work before she had a baby, mainly for donation, if i want to keep some im welcome to, I kept some for me, donated some and used the good quality stuff to sew a suit that looks rich. This suit is made out of that suit, I spent about a month on, I added my initials to handcuff stitching, buttons, its probably my favorite 'go to work, fuck you i have a lawyer and im better' outfit i made. I wear it and it looks just beautiful. I am good at tailoring stuff to my figure

She was over today, and she checks out my closet once in awhile. She sees the suit and she wants it back. She is insisting on remembering how much she paid for it, it never should have been in the pile she gave me, she tried it on, of course it looks great on her and we do have the same initials and she's going back to work soon, she needs work clothes.

I love that suit. I told her since she gave it away I tailored it to me, and no she cant have it. She is calling me greedy, I can tailor anything and it would look good on me, cant I just let her have the suit.

I don't want to part with it, I love it. AITA for telling her no, she cant have it. She was annoyed entire night after I told her I want to keep it.