You must add the friendly female assassin's entity name to the "m_szFriends" array of "CTalkMonster", assuming she's named "monster_hassassin_friendly", it should look like that:
char *CTalkMonster::m_szFriends[TLK_CFRIENDS] =
{
"monster_barney",
"monster_scientist",
"monster_sitting_scientist",
"monster_hassassin_friendly",
};
If your compile error is related to "TLK_CFRIENDS", you will have to find where this define is and increment it's value by one because this value defines the size of the "m_szFriends" array. In other words, if a basket is designed to carry 10 eggs maximum, you can't put 11 eggs or more in it.