Saw this movie about 20 years ago. It was in colour fantasy, and set in 1800 or 1900’s, when rich women wore big dresses and pirates were plundering.

 I cant remember much, but i remember a poor woman somehow  gets to visit this rich lady in a big mansion with a ballroom ect. And this rich lady gives or trades a fancy dress (May be 2)with the poor lady.  And then i remember they are in a mountain cave and there is a stream of water coming out of the mountain wall through a litle hole, and a flower of diamonds and rubies Come out of the hole and the poor lady gives it to the rich lady. And i remember there is a ball in the mansion, and i Think pirates Come and Rob them.