I used to go to group a wee while ago (hoping to get back to a new group this week). When I first started I found it easiest to find someone else who was by themselves and introdced myself, told them it was my first night and that I was feeling a bit nervous. Most people that go to group tend to be nice, so you should be fine!
Also, I'm veggie too! Slimming World is great for us veggies.