Make her change into something more appropriate.

"Go put on some real clothes" you say to her pointing at the door. She pouts and starts making a bunch of excuses but you are having none of it. She stamps her feet and makes a groan as she walks out to go change, you watch her huge ass sway as she goes. You continue to dress yourself, a big issue for yourself is that even your loosest pants still feel tight on whatever pant leg your enormous cock has to share a leg with. You eventually settle on some sweat pants, it looks like you are smuggling a baseball bat in your pants but it at least doesn't look like they are gonna tear with a single step.

Your sister arrives just as you finish getting dressed. She is wearing something that at least looks presentable but some how just as dirty. She has a sweater top of a white button up that is a bit to small for her massive breasts leaving her cleavage totally visible She. Her huge ass squeezed into some khakis that looks to be struggling to contain her curves which were tucked into a pair of high stocks fit into some cowboy boots. Most surprisingly of all she was wearing her glasses, which she practically had to be **** to put on. She runs into your room and does a little twirl showing off her body to you, showing you ever inch. "How is this?" Standing at attention in front of you with a expectant smile like a eager dog at attention.

"I look like such a prude." She says giggling like an airhead. "If this is what you like though I don't mind dressing like a nerd if that is what turns you on? So does your little fuck doll look good?"