My girlfriend left me to go back to her ex 3 weeks ago after being with me for 8 months.?

She only took a basket of clothes and her 5 yr old. She left her daughters baby book and a quilt her mom made her when she was a kid. She has only asked for her coat since she left. Do you think she will return? I am concerned about her because she is bi-polar and got off her meds about the time she left. Could that have been the reason she left in the first place?