More Sim behavior Questions

I think many of us just shrug and say, "Oh, those silly Sims."  It's really a nonsense game. Don't give yourself a headache trying to over analyze things. As for what happened with the nanny and grandma. Grandma is clearly an excentric and the nanny should be fired.  I no longer trust nannies. Any more I send the wee ones to Daycare. My Sims have come home to find the Nanny way too preoccupied with the bar, if you get my drift. Anymore, I cheat up the little ones' needs before I send the parents out and about. You can also turn off needs decay for them. (Although I have not had to do that in awhile.)

One thing I disklike about the game mechanics is that the household does basically nothing when you follow other Sims to where they're going. Or, if you have several households you play, the non-active household does nothing. They don't go to school or work. This I discovered when I sent the potential love-interest to visit the non-active home. I was totally shocked.

As for your townie being that high up on their career track, congratulations. You snagged an NPC meant to be there. Yeah, you got lucky.  Enjoy.

I have a story to tell about the aging up nonsense. Let me know if you wish to hear it. I was playing a Legacy Challenge at the time. It nearly derailed it.