Medical neglect is a serious form of child abuse and is defined as a "failure to provide or to allow needed care as recommended by a competent health care professional for a physical injury, illness, medical condition, or impairment" (source: www.childwelfare.gov). Last time I checked, religious or faith "healers" do not fall under the category of a "competent health care professional". It is even a form of abuse to delay the treatment.
So yes. Faith "healing" is both a form of child abuse, and an infringement on a child's fundamental liberties.