She was riveting in "Fallen"
I have to say, the scene where she wakes and her first immediate question of, "Did I kill anyone?" was amazing. She completely crushed that scene. I completely believed that character was a real person in that moment when she realizes all the horrible consequences to her friends and family, and the life she's built, and faced with the (almost) unforgiveable things she said to her sister. My opinion of Melissa as an actress was completely re-aligned by this episode. (full disclosure, I've only ever seen her in Supergirl)
Excellent job portraying the gradual growth of Kara into Bad Kara. Would be nice to see more of Confident Kara. Hopefully she won't always need Red Kryptonite for that!
Also, the shout-out to the Superman 3 scene, with the peanuts in the bar? Hah, excellent.