AITA for calling my brother's GF a diva?

My older brother's (23M) GF, Linda (24F) has been living with us since November after her parents kicked her out. She's really nice and we normally get along. She's a huge fashion girl and wears the most beautiful clothes, and she's been a great help for fashion advice.

Me (17F) and my younger brother and sister (13F) and (11F) were playing football out in the garden, and Linda was hanging out there too. As usual she was dressed her best. The ball ended up near her and I asked her to kick it back but she was wearing designer shoes.

''I'm not touching that thing with my shoes'' she said.

The ball was not dirty at all and I thought she was being silly, so I called her a diva and said tapping a ball wouldn't ruin her shoes. She just gave me a look and went inside, and later my brother had a go at me for being ''nasty'' to Linda.

How was that nasty? I asked her to tap the ball which wasn't dirty back to me. It wouldn't have done anything to her shoes. I don't see why she made such a fuss and was being a diva about it.