We have a problem

Lilah is now at a very interesting stage. She's independent and headstrong, constantly discovering new things and exploring. She is standing with ease and scooting along the furniture hesitantly. She has learned several new tricks. She can wave her hand, scrunch up her nose into a grimace, and has several words in her repertoire - "cat", "mama", "daddy", "num-num" (for food), and "no". Her top two teeth finally popped through the gums and are about half-way in.

All these changes have come with their own set of challenges, but Dano and I are at a loss for what to do with her now. The past week or so (getting progressively worse each day), Lilah has entered into a screaming phase. During meals, during a diaper change, mid-playtime, on parents' laps, while busy doing other things, in the car, whenever it strikes her fancy, Lilah Rose shrieks like a banshee. Sometimes there are tears, sometimes not. Sometimes it ceases when we pick her up and cuddle her. Sometimes she just beats her fists against our chests and screams all the more. There is no rhyme or reason to the behavior, no pattern we can see. No one thing soothes her, and I feel like it's out of frustration or for attention more often than not. She knows if we hear that high-pitched wail, we do whatever it takes to make it stop. I feel like the harder we work to make her quiet, the more often she does it! We've stopped feeding into it and started putting her in her crib for a cool-down instead. That has worked most consistently. Usually, she stops screaming her face off in under 5 minutes, and we retrieve her with praises and kisses. Sometimes, she wears herself out and falls asleep. We go by our doctor's recommended "20 minute" limit of how long to let a baby cry it out. Never let them from 0-6 months, and 20 minutes from 6-12. If she's still crying after 20 minutes, she often stops when we go get her.

I just don't understand. What turned our easy-going, never colicky baby into a devil child? Why is she doing it? She isn't hurt, all her needs are met, she isn't teething, so why the screams? What else can we do to make her stop? Why don't babies come with mute buttons?