Under normal circumstances you would never hit a girl, but under these circumstances you decide it's all right. Kristen clearly does not care about your fate in the slightest, and letting her gain the upper hand could result in her having the gun, and with it, total control over you and everything else. No, the best bet is to knock her off balance so you can make sure you still have all the power. So you sock her in the face, and she falls over with one punch. She's still conscious, and though her nose is bleeding, it doesn't look like anything's broken.
So there you are, both a quarter-inch tall, and you're still mad. You've had enough of being shrunk, at least for now, but you want to think of the cruelest possible punishment for Kristen back when you've returned to regular size. Part of you wants to make her watch as you turn into an exact replica of her and take over her life. You could walk around all day acting as Kristen, with no one the wiser. You could even keep the real Kristen tiny and put her in your cleavage to tell you how to act so you can fool everyone.
Of course, part of you just wants to make her your sex slave.