Much of this movement is to regulate the contents of the cell. This includes bringing material into the cell from the extracellular environment or the plasma membrane (endocytosis) or releasing material made within the the cell to the outside (exocytosis).
It really is an easy project...it just takes a little time. All and all, it took me about 6-8 total hours to make 4 bouquets, 10 bouts (my mom made those though) and about 15 centerpieces. I made two bouquets the day before our wedding and the other two the day of the wedding.
Wedding invitations are usually sent out 8 to 10 weeks before the wedding. So it is typical for the shower invitations to go out before the wedding invitations. If it makes more sense to send the shower invitations before the wedding invitations, then that's what she should do.