Haha I feel both of these options will lead to Walter being extremely sus about her acting abilities!

Both options sound like good fun- she'd be a bit skittish about showing him her skills with a firearm, but once they're actually sucked into the FPS her combat instincts would overwrite her 'Junko' act. I think they'd have a good chance at the high score.

Of course she'd also be a little too interested in hearing his war stories if you'd rather go that route.