AITJ for refusing to pay for my sister’s wedding dress even though I could afford it?

I recently got a significant raise and have been managing my finances responsibly (no debt, healthy savings). My older sister is planning her wedding and picked out a very expensive dress. Without asking, my mom suggested I cover part of the cost since “I’m doing well.”

I said no, if she wants a pricey dress, she should handle it or choose something in budget. My sister exploded, calling me jealous and selfish for not helping. My mom guilt-tripped me, “Family supports each other.”

They’re now painting me as the bad sibling. I feel pressured but I also believe I shouldn’t be forced to bankroll others’ luxury choices.