@Doenyon Forget what was being said about ephemeral otaku memories, because that was kind of off the mark as far as I'm concerned. I'd say it's more like she had the knowledge to barely survive a fight with a specific type of enemy and end up injured and unconscious for 5 days due to dumb luck. Now? She wants to train so she's actually good at this stuff in a much more broad, and general scope and won't get laid up for a week or so every time she fights anything, or worse. She's being smart and preparing for the future.
If you really think she's already skilled enough to survive future battles, go look at her terrible aim again with her slingshot there. First head shot? Dumb luck. Shot to a hip, no real effect. Shot the ground, wasted time and ammo. Hit a throat, dumb luck plus being much closer to the target. Not really a super skillful showing, was it?