The companions were NPCs?
Yes, as Lord Fellgrin points out they were NPCs. She was the only player in these sessions and in the "Keep on the Borderlands" module it says that if you rescue the two "Men at arms" in the Hobgoblin prison they'll vow to work for the PCs for "a year and a day" without demanding money other than room and board (or something like that. I may have improvised some of it.)
Also in basic D&D (and I'm sure in AD&D as well) there are rules for hiring "Retainers, Hirelings or Henchmen" which are NPCs who help in the battle, require payment and otherwise are loyal to the PC. There's a loyalty base score and a chart that will determine how loyal they remain, of course, with modifiers based on how they're treated. Buying them gifts, for example, definitely put Tulip way up in their esteem.
The CHA stat has a "Max Henchmen" and "Loyalty Base" score after it in both systems.