I've been in the same boat as you! I am someone who would prefer to just do everything on my own so that I can get the grade that I personally deserve.
My A&P group decided that we would all do case studies separately, and then e-mail our results to each other. The first time, I typed them up. It was due on a Tuesday, so I had it done by Friday night. I e-mailed my results to everyone and waited. Monday night at 9:30pm came and I got responses from 2/3 other people in my group. One contributed, the other person just wrote, "I pretty much got the same answers as you, and I don't feel like uploading them if I don't have to!" This was the same partner who would constantly try to copy my work in lab.
The next time, someone else offered to type up the case study. You don't even know how nervous I was! I e-mailed the girl like 6 times with my answers. Then she sent back the final draft and she had it formated all wrong (which was important for our grades). I told her what she did, but I was so afraid that she wouldn't see the e-mail that I ended up printing it out for myself. She thought I was so weird!
The whole class seemed to have this problem a lot. One group actually kicked another girl out of their group and the teacher agreed. The girl never contributed to the case studies (though she swore her grandma kept dying and that they were deleting her e-mails and stuff..every excuse in the book). We got a laugh out of her complaining that she had to do everything on her own, and she ended up flunking the class (no wonder).
I think the best thing to do would be to give them a chance. If you are working on a project, and someone does not contribute AT ALL, then don't put their name on the project! Your teacher will most likely only grade for the people listed on the project. If you feel like a grade misrepresents you because of the poor work from your group mates, ask your teacher if you could maybe redo it on your own and explain the situation. She may put you in a different group or do something to change the situation!
Good luck! If you're like me, you're the kind of person who will NEVER be put in a good group because I really just can't stand them to begin with! Teamwork in the work place is great, but as soon as it comes to something I'm going to be judged for, no way!