@dexterbeng I would guess 15-30 seconds. pm2 has to detect that the process has terminated and restart. It depends on the polling interval for pm2 (which, as far as I can tell from their docs/issues, is 100ms, and cannot be changed – seems more frequent than I expected).
Why are you killing mm with Ctrl+Q? Better to use pm2 restart mm or even pm2 start mm --watch which will also restart mm after file system changes (you may need to configure which directories to watch).