Basically, you can lay in wet grass but the air is dry
Having heat from above kills your humidity in the air. With that kind of setup , you will always fight this.
I think the snake has enough "humidity" down below in the substrate, but you can't have it all wet either. Give her wetter "areas" in both cool and dry area (harder to do in small setup) and keep the lid as enclosed as you can.
You could put a wet paper towel on the screen and then aluminium foil above that, to keep the air from above drying out the paper towel and to keep the humidity inside of the tank for as long as possible.
Measuring humidity is tricky, and the probes are temperamental..many things can throw the readings off. I think what you get is fine for now, keep misting lightly, but don't saturate the substrate. You will just have "more work" (misting) with the glass tank, but you are doing great so far.
If you do a little bit of research how the humidity probes and readers work, you will see what I mean..
Just breathe, and enjoy your little snake, she is a BEAUTY, and wow, already ate for you
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