Group Effort - or not?

I have worked in several group projects and have all yet been successful. This group project has been satisfactory when it comes to maximum effort. Our fellow group member, Samantha Gaber, has failed to complete mandatory assignments which tipped the scale towards our grades. Despite our grade drop, there has been strengths in our group's effort. Valeria and myself dedicate and value this website beach project. However, Samantha does not show responsibility when we tell her the little assaignments she needs to do. If we were to have a successfull group, all of the members show equal responsibilities in the work they have to do. Samantha continuously is reminded to do her work, where she claims she forgot to do so. Because of her, our grades are not as pleasing to those groups with responsible members.