I once called daily trying to get a reservation for my DD. Some of the CMs even began to recognize me, lol. Eventually something did open up. I’m not sure how common it is for that to happen, but plans change and people do cancel, so calling might be worth it. The Disney Springs location usually has more availability so if you can be flexible, you might get in there more easily.
Another option to consider is the Pirates League. They do a mermaid package that is quite special (I did it myself!). Also a girl pirate- the Empress- which is also a great experience. My daughter really enjoyed it last month!
Also some of the deluxe resorts with salons are now offering a “character couture makeover”. It’s more expensive than BBB, but I was able to get a reservation for my daughter last week (Ivy Trellis Salon at the GF) at approximately 35 days out. Good luck!