i don't think we acknowledge this enough when it comes to legend of korra s3 but Lin was MORE than justified in cutting off Su. like her history PERMANENTLY scarred her face for the rest of her life and their mother just brushed it under the rug and not to mention how Su plays dirty in arguments like bringing up her and Tenzins breakup which was most definitely a really sore subject just so she could get her sister to be emotional

tldr: Lin is the greatest character ever and i love her dearly