If you can still return it, do so and get some rock cave hides or just head to the dollar store for some plastic bowls. Half log hides don't make good hides for ball pythons, that is probably why you noticed her not using it as much.
If you want the realistic viv, use the rock cave hides. Then you won't have the sap issue. As for disinfecting them again, you don't need to put it in the oven for so long. 30 minutes on 250* is plenty. You could also boil it if you have a big enough pot.