In mid August I was commissioned by someone who has commissioned me before. She always paid in full and reliably, and this time requested a rush order. I agreed, but because she does not use Paypal I started on the commission immediately to get it done by when we agreed rather than wait for payment to arrive (although this is literally the only case in which I've done this. I never work on a plushie at ALL unless I at least have a deposit, but she had been reliable in the past.)
I had the plushie done by the due date and emailed her a number of times, but she did not reply. Finally, by the end of the month she did, stating that she had been busy. She requested a couple changes (which would have been a piece of cake to make, but I asked for clarification on them because they were a little unclear) and she asked for my address. :/
Well, she didn't reply until the end of September. She asked if she could send half now and half later since she had to buy something for her cat's flea medication recently. She said I didn't have to send anything until it was paid in full (I wouldn't anyway) and I said that was fine and everything. Once again, she didn't respond, this time until mid October. This time stating that her dog had hip problems and she couldn't afford to pay me but would let me know when she could.
I said okay. Whatever, although getting sort of annoyed because it's been months now -- no money to show for it at all, I pushed back my normal commissions to work on hers as a rush order, etc. I emailed her again this week and I still haven't gotten a reply.
I don't know what to do at this point. :/ Like I said, she's been reliable in the past, so I don't want to get too angry or anything and she has generally been really nice but... this is getting kind of silly.
Edit: This has been resolved, thank you for all the great advice though. It's all very useful & important stuff to keep in mind in the future.