Push the woman off of you and demand an explanation.
From Create Your Own Story
You fling the woman off of you, grab the gun, and stand up quickly, pointing the weapon in her direction.
"What the fuck!?" You demand, shaking the gun. "You're infected?!" She nods. "Then why'd you gather all this shit? Let me think we could survive in here?"
"I found this place," she says with a shrug. "After I realized I was infected, I came here and found the vault. I shot the guy who was in it. When I found you knocking on the door, I was actually dragging his body out. I'm not a very good person either."
"You've got to be kidding me!" You say, still in shock.
"Nope," she says, reaching down to lift up her hoodie enough to give you a view of her belly, which is peppered with several red spots. "I'm infected. Now you are too. Not like you don't deserve it, so don't act all fucking high and mighty."