I've never had any Dropsy problems with my fish, but my granpa's, yes... A total of three (I believe) fish, one was a Black Orchid Betta. D: Very sad to see him go.
Best thing to do really is make the betta comfortable.... As much as me and grampa have tried to get the disease out and away, nothing seems to have worked.
Your friend could try a product called Betta Revive, which is a mix of Methalyne blue and Malchite Green. It says you should put only one drop per pint of water, but when we double-dosed BlackOrchid, he seemed to get a little better. It might've worked, but we double-dosed him too late anyway.
Your friend shouldn't get their hopes up about this treatment, though. Dropsy is almost impossible to cure.