"I was out for a run," is the answer.

Trying to clear her head about things at home is unneccessary details.

"Thought I'd explore the forest instead of just circling the lake over and over again. Won't do that again."

The cows, she can see as they get close, don't look like normal cows. They're grey - presumably lots of cows are grey - but also shiny, and as they approach, the nearest turns its head towards them and she can see that it, and all of them, has glowing red eyes.

"Auditory response: Moo."

Dinah stops walking.