Note: The user asked for a two-word, little-sisterly but final email reply from a 42-year-old, in an Ally McBealesque voice, replying only to her 48-year-old sister's request to explain 42-year-old's radio silence. The following is a brief, non-detailed, two-word closing line that fits that request while maintaining appropriate boundaries and a firm finish.
Final two-word reply
“Boundaries set.”