She was very drunk. It would be very difficult for her to negotiate her way to the river over rough ground. Even harder from her home or anywhere on the quickest route to that home as per the claims made by PRs sister about his actions that night.
Why do you take what PR sister said as fact??
1... English is not her first language something could have got lost in translation
2...Even if PR told her that it's probably not the truth.
3...It came from the red tops, notorious for printing half truths.