I have a client that I had photographed her lookbook for her in which she has signed my contract and paid the deposit fee. A day after the due date of the invoice I had messaged her of the status of the invoice. She replied saying one of her clients hasn't paid her so she can't yet pay me. She also said that she would pay half the first week and the second half the second week. As I thought I'd be lenient i agreed. However after the first week, I had not recieved anything so i messaged her and yet no reply and left on seen. The second week came around and still no payment and again, left on seen. It's now been 19 days since the due date of the invoice and I'd love to know your thoughts on what to do in this situation. I'm based in Australia.