Confidence! Just try to keep calm and take a few deep breaths if you need them... Let your sis know how you're feeling if it makes you feel any safer. You have to keep a positive mindset and just keep relaxed... What most people will notice is confidence, (Trust me.. confidence does a LOT more than 40 pounds of make-up can...) If you think you hear people commenting or looking funny, remember half the time it's really your mind playing tricks on you, that or they really aren't worth the attention. If you think you're a star, people will see you as a star
Took me a long time to realize this... So yep, chin up and smile, you can do it!

PS: The captcha insists violets are blue... But I could swear they are purple, hehe..