Thanks Deborah,
She hasn't whistled at all today, and I haven't found any mucus nor have I seen her mouth breathing, so I think she's alright - thank goodness.
I dampened a towel and placed it on one half of the mesh, and it seems to be keeping humidity quite well.
I'm currently waiting for the 250w CHE to heat up the hot side to see what adjustments I need to make to create a good temperature gradient
Thanks again for all the comments, I'll be sure to post some pictures of the tank when it's fully decorated and set up
https://i.imgur.com/LC7qFeB.jpg
Bonus pic