The place isn't really that big. And it would have had to be armed by Wright who was in the lab with Mackenzie (Mack certainly wouldn't remember how to disarm a bomb so she'd leave it to Val to do it).
Her body does whatever it can to keep her from dying. If she has internal bleeding, her body stops it instantly. If she goes into severe shock, her body kicks into gear to heal itself until it is no longer in danger of dying. If both of her lungs are punctured or bowels are perforated (ew, and ow) or her heart or any other vital organ is lacerated, her body kicks into full gear. Going by this theory, she should be able to survive a shot to the head as long as the bullet doesn't enter/damage the region of her brain that her power uses to heal her body. An injury to the brain would most definately heal instantaneously.
If she breaks her arm or her leg or gets skin scraped from her face or her ear gets ripped off, or any other non-lethal injury, her body will not jump into action. It will heal faster than everyone else, but it will not be instantaneous like wolverine. She can probably heal a major broken bone (i.e. femur) in about a week's time. Small breaks take shorter amounts of time. Scraped skin will probably heal in a few hours. Cuts and lacerations to the skin would be gone by the next day or two.
She has nerve endings. She can feel every ounce of pain from every injury she gets. Her body just won't let her die from the shock of said pain, which probably has something to do with it dumping extreme amounts of adrenaline into her system to keep her aware and alive. It also allows her to fight through the pain immediately after injury occurs (i.e. crawling out from under a bombed building to throw a brick at some guy's head). I'm thinking that the additional adrenaline kick, more than most people would get even in a life and death situation, could be classified as a secondary power, although she'd probably have to go through extensive lab testing to get it proven and legally identified as a power. And who wants to go through that much of a headache?
I hope this is clear enough. If it isn't, please ask any specific questions about her power than you don't understand. I promise to have an answer, even if I have to pull it out of my butt as I type it.
edit: this post is far more entertaining if read aloud in an English accent.