@shyevsa well, is the first town, everyone is a noob and everyone has their guard down because of it, and I don't think this game is based on HP for life, if you go for the neck, lvl 1 or 100 they'll die soon... If she kills 3 people she's most likely going to lvl up and be stronger than most people there still trying to take the first quest.....BUT, I know is BS to cut clean someone's head, you need a big amount of force.........but this can be explained by the use of an unique skill for assassin where normal logic doesn't apply.
She got away easily because there were no archers or wizards or anyone skilled enough...and the fact that she goes for the kill without hesitation against humans and that's an incredible advantage.
This is a girl going in a killer spree inside a game, it says so in the synopsis, if you were surprised by the lack of plot or motivation beyond self satisfaction.......is your fault lol, I find this actually hilarious and interesting enough, like, I feel like she could become someone dangerous enough to have the GM involved and I want to see that.