As a Christian myself, I do not understand these kinds of people.
I mean, if you want to believe in faith healing, fine, that's your choice. Personally I've never witnessed a successful case of it, but I'm willing to believe it could happen.
To rely wholly on faith healing and ignore doctors and hospitals completely is idiotic, however.
Let the doctors do their work, and pray for their success and the health of your loved one. Whether they are healed through the doctor's efforts, divine intervention, or some combination thereof, what does it matter so long as they are healed? That's how I see it anyway.