No, terracotta has a slightly rough texture, which will help Matilda get in and out easily, and it is also relatively heavy. You can get them easily from garden centres, . I'm sorry, I should have made it clearer.
If you can rig up a wooden framework above your table, you can drape a sheet of plastic over it , which will hold in the humidity. I'm sure you will get things sorted out soon, and that you will see an improvement. I would also suggest you spray her food during the day, as it looks a bit wilted - it will help get fluid into her.
Angie x