UPDATE:
Stewie has been found!! She was curled up in my mom's underwear drawer..where I did look before, so she must've just moved there. But, she was looking rather hungry, and it's three days past her usual feeding day, so I gave her a mouse and she ate it without hesitation. I'm so happy and relieved that words cannot describe it...and from this, I've learned: you certainly can't trust just anyone with your snakes.