Yeah, so it would make sense a bit to build up from here as well. Specially, if you have the option to pick was the best body and the choice to pick Ellie
For you, would stripping your sister of her clothes, evaluating her body, and making choices her in front of her friends help you and your sister develop a relationship?
Moreover, you have made mistakes with your sister many times, or have done things she does not want, and your sister despises you by calling you a pervert. Does that really help?
If it were me, instead of undressing her in front of her friends or, conversely, undressing her friends in front of her, I would talk to her, apologize to her, and take her out for a meal.
I think this is common and normal.
And it is true that this is common and normal.