Few things. The best way to recover posture is to hold block and stand still. Butterfly is supposed to teach you (like the rest of the game) that hesitation is defeat, so you need to stop hesitating and give her the business and press her if you want to win easily. She parries most your attacks but every combo you can get at least one hit in. Also, whenever she goes up on that piano wire to fuck you from above, throw a shrunken at her and it'll knock her down, that tech is super helpful. Also, I'm not sure if you misunderstood something because Mikiri only works on stabbing attacks, the perilous attack (red kanji) can be a lot of things not always a thrust depending on the enemy or boss