Which UnitPopUp.lua contains the menu, you are talking of?
I extracted Interface\FrameXML\UnitPopup.lua out of interface.MPQ and it contains the following menus:
Code:
UnitPopupMenus = { };
UnitPopupMenus["SELF"] = { "FREE_FOR_ALL", "ROUND_ROBIN", "MASTER_LOOTER", "GROUP_LOOT", "NEED_BEFORE_GREED", "LOOT_THRESHOLD", "LOOT_PROMOTE", "LEAVE", "CANCEL" };
UnitPopupMenus["PET"] = { "PET_PAPERDOLL", "PET_ABANDON", "CANCEL" };
UnitPopupMenus["PET_RENAME"] = { "PET_PAPERDOLL", "PET_RENAME", "PET_ABANDON", "CANCEL" };
UnitPopupMenus["PET_NOABANDON"] = { "PET_DISMISS", "CANCEL" };
UnitPopupMenus["PARTY"] = { "PROMOTE", "LOOT_PROMOTE", "UNINVITE", "INSPECT", "TRADE", "FOLLOW", "DUEL", "CANCEL" };
UnitPopupMenus["PLAYER"] = { "INSPECT", "INVITE", "TRADE", "FOLLOW", "DUEL", "CANCEL" };
UnitPopupMenus["RAID"] = { "RAID_LEADER", "RAID_PROMOTE", "RAID_DEMOTE", "LOOT_PROMOTE", "RAID_REMOVE", "CANCEL" };
There is no FRIEND menu.
EDIT: I found it. It is in patch.MPQ, not in interface.MPQ.