Thank you both for your replies!

I would never leave Lexi (cat) unattended in my room. It would be a disaster waiting to happen. Not saying that she would be too interested in attacking the snakes (though i would fear her trying to intimidate them, anyway), but I also have many, many knick-knacks and random breakables on shelves. She's young, so she would have a field day if I left her in the room alone!

This morning, I think Marley scared her. She was staring at him through the temporary tub he's in and he rested his head on the water dish so that he appeared to be staring directly into her eyes. I'd heard that cats dislike being stared at, and I've stared at Lexi to test the theory. She certainly does seem to get fairly insecure/uncomfortable. Marley maintained that position for about 10-20 minutes, and Lexi was doing all sorts of things to make him stop. Ducking so that he couldn't see her, walking a few steps away...he must've been in "rest mode," because he didn't move at all. Finally she took off and hasn't looked at him since. He's moved around since then, of course, but even when he was moving, she gave a very quick .01 second glance and went about her business.

Again, thank you both for the input!