mc Donalds is the kind of place where managers worth their salt know and expect that their employees will bounce as soon as they find better employement elsewhere.
I wouldn't be surprised if that was actually an expectation their recruiters consider a positive trait..because it means you are ambitious and want to do better..which will make you be a good employee for as long as you stay with them. Mcdonalds and such have a high rotation of I doubt your managers will think any worse of you than of anybody else.
that said, I would have stopped in front of colleague and managers and asked her flat out what her reasons were for lying.