You could wear them over jeans with a nice blouse and a jacket over that, a tee shirt dress or a skater skirt with a crop top. I'm not sure how well they would be to wear to a club I've never been to one but I'd assume it would get pretty hot in one and leather boots to me personally lock in heat easily so it might not be the best idea if you're going to be dancing and what not. However, those boots can be dressed up for a club just as easily as they can be worn more casual.
It gets really hot and steamy in clubs, you may look good but be uncomfortable is all. I'd wear ankle boots open toe heels or flats. Clubs are already heated and it's filled with sweaty bodies. You're better off with something cooler but if you're not going to do a lot of dancing.. then sure go for it.
Love them and do not know why your sister do not want them. I have a pair like that that I wear to clubs and parties. I wear either a mini skirt or a tight dress. Sometimes leather leggings. They're great boots.