Based on the error message, the headers in your csv are actually: Group Email [Required],Member Email,Member Type,Member Role
So, instead of ~GroupEmail you would need ~"Group Email [Required]".
Another issue that I see is that your command still will not produce the results you want. You'll want 2 csv's; one with the groups that you want to create, and another with the members. The headers of the first should have headers like GroupEmail, GroupName, and any other headers you'd like to customize the group with. You would then run this command:
gam csv creategroups.csv gam create group ~GroupEmail name ~GroupName.
You can then use your existing CSV to populate the created groups with the members you'd like to add. There are a few options, but assuming you just want to add members, this should work:
gam csv newgroupsclasses.csv gam update group ~"Group Email [Required]" add member ~"Member Email"