The whole thing was dumb on her part--I thought she'd be smart enough not to be goaded into a situation like this. After all, it's at the height of folly to gamble what you can not afford to lose--and that's exactly what she did.
I hope she doesn't get put on a bus, though--I like Karen. She is loyal (though she could stand to be smarter about it), and she's cute and pretty--in spite of that short haircut. That uniform looks quite good on her, and she wears thighhighs well--and they're seemingly part of her style, which is a plus.
Now, what I want to see is that Guren isn't your average, milquetoast Japanese MC, and will properly give Mizuha what she deserves for repaying his kindness with transgression against his sister of all people. If I recall correctly, he didn't take such a thing lightly. I wonder if he will now, now that there's an opportunity to show what happens to people who mess with that sister of his he claims to value.