Check everywhere and all over the room and any nearby areas. Check every space that you think she's most likely to fit through, even places you think she couldn't fit through. Definitely check around warm areas. I'd shut the door to the room and put something under the door to block the snake from slipping through.

What also helps is thawing out a rodent. You can put it on top of a plastic bag which makes a lot of noise. So thaw out the rodent, place it in/on the bag, make sure its completely dark in the room, and check in every now and then in case you see her on the floor anywhere or even on the bag eating the rodent.