This situation is absolutely terrifying me...?

Well the whole hygiene thing, I mean that can be handled. There's no excuse for smelling bad. Shower, spray yourself, brush your teeth, wear CLEAN clothes, do all that you can to keep away from the bad scent because no one would want to be around someone with bad hygiene! As far as looks, you need to keep a positive attitude and be confident. Listen to some music that makes you HAPPY, something that boosts your esteem. Listening to "dark" music won't do you any good. If you find that you are overweight, do something! Work out, I know it may be easy for me to say, but if you're THIS uncomfortable with yourself, complaining and coming to Yahoo! Answers won't do you too much. Try a good shake or something - HerbaLife is an amazing one that gets you results quickly. Just be yourself tommorrow, show her who you are, try to be the same person as you are on Facebook. Be happy, confident, because it will truly set out a much more brighter array when you guys are together. Don't worry, have fun and enjoy yourself. Things will be fine, goodluck!