Place a basking light in the area, because she is likely to get cold in the basement. It may lure her out to warm herself up. Food could also be a good lure, since she will eventually get hungry. My bet is on the basking area though, balls can go a long time without eating if they are so inclined.
Other than that, keep looking in and around and under everything. Even check the rest of the house, look up if there's anything she might have been able to climb. If there's anything I've learned about snakes is you'll find them in the most pain in the butt place to retrieve them from. Heating/air ducts, under/in major appliances, etc. I was lucky with my last escapee, she was trying to climb into the baseboard heater when found. :-/ That could have been ugly.
If you have windows in your basement, check for any places where she may have gotten outside. This also applies if your washer and dryer are down there. Plug any sink, the vent for the dryer, drains in the floor, etc.
Good luck, and I'll keep my fingers crossed for you.
~L~