Apparently I am incapable of operating the volume control on the baby monitor because, despite checking that it was turned up enough to hear Abby, it wasn't. In my stubbornness, though, I actually checked the volume in the midst of seeing the lights go off for sound as no sound was coming out.
The reason I woke up to Abby wanting a 3:45 a.m. snack was Leia's prompting. I was proud of her for getting me up, though her train of thought for actually doing so has endless possibilities.
Scenario 1 (the superhero scenario): "Hmm. I hear the child crying, but there is no movement from Mom's bedroom. I'll alert her." ::begin mewing::
Scenario 2 (the random thought scenario): "Hmm. I hear the child crying. You know ... I'm hungry." ::begin mewing::
Scenario 3 (the sinister plot scenario): "Hmm. I hear the child crying. I don't understand why she's the only one who is fed at her beck and call. I'm going to cry, too." ::begin mewing::
However the process worked in Leia's kitty brain, all worked out in the end. My inability to use a baby monitor was overcome by one swell kitty.