Sorry about that. You are correct, the file is in /administrator/language/en_GB/en-GB.plg_socialprofiles_jomsocial.ini That's where Joomla stores the language files for all plugins, even if they operate on the front-end.
Glad you found it though, and if you have any other questions, just let us know.
Finally, if you haven't already, please consider leaving a rating and review for JFBConnect, or our support, on the Joomla Extension Directory. It certainly isn't required, but is very appreciated:
extensions.joomla.org/extensions/social-...ook-integration/7215
Thanks,
Alex