Wow. You remind me of myself when I met my current boyfriend for the first time. Long story short, we met online and after a year of chatting, writing letters and talking on the phone, decided to meet. He had seen pics of me and I had of him and like you said, it's so easy to make yourself look different in pictures than real life. When we saw each other, there was an awkward silence. Lol. He saw that I was so heavy (I weighed 184 lbs at that time) and he was really, really skinny. A few minutes of talking later we realized that we loved each other too much to just stop seeing each other because we both looked different from each others' expectations, you know? It's been a little more than 6 years since and we're still going strong
What I'm saying is, relax. There probably isn't any bigger turn off for anyone, guy or girl, than insecurity. If you guys already have a deep connection going on and if it's true, the weight might come as a surprise but it shouldn't interfere with having a great time with her. Just be yourself, relax and have the time of your life. Anything that's bound to happen will happen (if you believe in fate). If she senses that you're nervous about your weight, it might make things awkward. So relax.