Well, ball pythons are very shy snakes. Removing a hide so that you can see her better will just make her less willing to eat. These snakes will hide all the time if they had the choice.

The strip thermometers are meant to measure the temperature of water, not air. So whatever you think your temps are, they are not. Using a UTH unregulated is pretty unsafe. They can get up to 120* which is enough to burn or cook your animal. If your temps are off, that could be enough to make your snake go off feed.

I would think about moving her to a smaller tank or a plastic container. These are secretive snakes and thrive in smaller cramped spaces. I would only use a 30g long for a particularly large female (over 2,500 grams).

How big are the cardboard hides in relation to the snakes body? They should be very tight fitting and touch the snake on all sides. I use plastic cereal bowls from the dollar store. They come in four packs so that is four hides for $1! The cardboard hides will need to be tossed every time the snake goes to the bathroom.

Stick with the aspen. Reusable substrate is just not worth the effort of trying to get it clean. After a while, it will be impossible to get the smell out, which means bacteria is going to grow in it.