Because the PC area was where she was setting up. Why park at the front, walk through the building to unlock, then back again to get back in the truck and drive around to the PC? Extra, unnecessary driving steps. And as far as leaving the truck parked out front, there's no awning over the main entrance to protect any electronics. Even if there was, why lug all the equipment from the main door area, through the building, to set up in the PC area? It makes perfect sense to park under cover of the PC where you're setting up, walk around to unlock the doors, then unload.
As far those concerned what the weather was like - oddly, some humans are not afraid of raindrops. I know this may sound bizarre, but it's just water. If you're dressed in workout clothing and you're going to be covered in sweat shortly anyway, I don't see anything unusual about walking around the outside of the building in the rain. I walk in the rain all the time. I notice lots of people seem freaked out by it, though. I've seen people actually panic and hurt themselves trying to avoid rain. Just seems odd. X)