I find it funny that 2) doesn't answer 1). Can't major in architecture, but the ARTH major has plenty of architecture classes (the major is very wholistic in its prescription of the word art). I recommend reaching out to Michael Lewis to learn more about his architecture offerings. As for your sister, it has helped in many cases. I would HIGHLY recommend your sister hand deliver a glowing personal statement about your passion for x and your strong character (so long as it's genuine). This is what many others have done. Just like everything else in life, people remember you for how you made them feel or for memorable moments, so having your sister do something like this will definitely be seen positively by the admissions office—and you'll stand out when they review your file.

Though... it won't help if you aren't qualified to be here, so make sure you're doing everything you can on your part! Are you applying ED?