I'm not going to constantly tell a group member to do their work
Why aren't you telling them to work?
I am not going to push them to do their work
If it's not your responsibility to make sure their work gets done, then don't worry about it! It's ultimately up to them how they want to contribute. As long as you do your part, you have nothing to worry about.
I can't work with them if they are going to be like that.
You shouldn't let how others work detract from how you work yourself.  If this is such a problem for you, speak to your manager about transferring to a different department or workgroup.  You might be less stressed out then!