First off, the ladies that have already responded have excellent advice....
... and this is where I'm going to get tough.
We have some similar stats you and I -- 5'11" with a wedding in 2 months. I don't carry weight around my midsection either so I can assume that we're probably fairly similar in shape (that's never
happened in real life with me)
. Sure it'd be awesome to be 160 or 150 even, but I bet you anything that you are absolutely stunning as it is!! It's really just a big mind game in the end as no one sees the little imperfections that we see on ourselves.
So for the next couple months focus on what makes you feel good about yourself. I find weight training does the trick because it makes me less jiggly and I get to see muscles defining themselves. Drink lots and lots of water every day to get rid of any bloating that's going on that makes everything feel a little tight. And you know what not to eat... anything that makes you feel bad about yourself! Get all the nourishment you can out of your food and fill up on good-for-you things and you will feel like a million bucks.
So even if you don't really lose anything for your sister's wedding, it won't matter! Naturally, your skin will be better, you will feel more energetic, and you'll be able to strut because you're a knock-out.
(make sure you get some awesome heels)
Good luck hun, i'm in the same boat so I know exactly what you're going through. And today I was actually called "thin" so that's friggin awesome. (and I'm 10 lbs more than you!) Have fun!