Black and white vintage film (30’s/40’s).
Scenes remembered: After picking up her sister’s glamorous dress (gold lame?) at a shop, she wears it to a party to seduce the sister’s lover. Oblivious to the fact that the gown it too big and falling off, she causes an embarrassing scene as she passes through the crowded room.
“A Stolen Life”(1946)?
It has the dress scene and stars Bette Davis.