Trouble Settling In?

I have two cats they have always gotten along very well (slept, play, ate together). Unfortunately I had to leave one at my parent's house because she had run away and I had to drive two hours to get to work on time. A week later I went back to get her, since that time she hasn't been the same. She won't play or sleep with the other cat and eats much less. What could be wrong? Is she just trying to get to normal again? It's been about a week and a half since she has been back.

Cats don't like change, so I would say give her some time.  She needs to adjust to the new surroundings.  How long was she outside when she ran away?  Had she been to her vet to make sure she was OK since then?  You can try Comfort Zone/Feliway diffusers.  They could help in a situation like this.