If you want to get a good grade for the course, you ll need to get a good grade for the project. In a short semester, if you fall behind it is hard to catch up. It is inevitable that there will be some disagreements between members of your group. When these disagreements arise, try and find a reasonable compromise. Only bring group problems to the teaching assistant after you have tried to fix them yourself.
Some people like to work a lot harder than others.
If this is a major problem within your group, then bring it to the attention of your teaching assistant as soon as you can. However, if you do so, make sure that you are able to back up your claims. Before bringing the problem to your teaching assistant, try and fix it within your group. See of you can get them to change their work habits. Give them a chance to complete a reasonable deliverable.