My main concern with the trashbags is the texture. My snakes get freaked out by the texture of certain types of carpet even and can be weird about going onto new surfaces, so I would worry that she'd just not touch the trashbags at all.

If you can make the area you think she's in cool and create a hotspot that might work. It doesn't have to be excessively cold or anything, just enough that she'd be drawn to the hotspot.