After a bit of research, I've come up with a few possible purposes/meanings for this sculpture. The first of these theories is that she is a representation of charity. Charity was usually represented by a statue nursing an infant or getting ready to nurse an infant, so I'm less inclined to think that this was the intention of the sculptor. Sometimes exposed breasts were meant to be a nod to motherly love, protection, devotion, etc. This may be true, but I don't feel that the statue is entirely motherly in nature. The third option and the most likely, in my opinion, is that this statue was meant to portray a mourner. The woman's hand rests on her face, and her entire posture suggests that she is not meant to seem happy. To me, she looks tired, desolate, dreary; clearly, she was meant to stand as a testament to how much this person was missed. She also holds a funeral wreath that says to me (but I'm not sure) that her purpose is a mourner above all else. The exposed breast may suggest nothing more than the sculptor or family's love of ancient Greece, or the statue may be going a step further to perhaps try to show that the mourner exudes a more motherly and tender approach to her grief.
I love being able to reach multiple interpretations for the intent behind a sculpture! Hearing other people's perceptions is also very interesting!