You pause for a second to take a look around at the unbelievable magnitude of your surroundings. This proves to be a terrible mistake, as Kristen grabs the gun right out of your hand. This time you don't hesitate, and you run like hell.
You are very fortunate that Kristen's dorm room is tightly packed with furniture and is not especially clean. You first run underneath her dresser, and you quickly hide behind an errant tube of lipstick that had rolled underneath. You hear Kristen coming up fast behind you, and you decide not to stay put in one spot. You hear her running one way, and you run the other, eventually coming out on the other side of the dresser. You find yourself marginally closer to the door out of Kristen's room, and all you have to do is run behind her clothes hamper. You don't want to abandon the gun with Kristen while you're stuck in this shrunken state, but maybe it's better under these circumstances to retreat now and retrieve the gun again later. It's not like you'll be easy to see when you sneak back in.
To her credit, Kristen has finally realized that she should stop chasing you and just use the gun. If she just shrinks everything you're hiding behind, it'll be a lot easier to catch you. Although she knows you'll escape her room if she doesn't hit you with the gun soon, she stops to look at the settings. She stands still for a few moments and decides what she should do.