They are appointed whenever an interest of a child needs protecting. The most common being child-abuse, foster care, adoption, divorce, child custody (family law) situations. Those are all civil, not criminal.
Here, I notice that the civil suit appears to have been filed by the guardian ad litem - at least that is what the article below says. While I understand why some want to see evidence, I will say (I'm an attorney) that a suit filed by a "non-interested" party, like a guardian ad litem, carries a lot more weight than one filed by, say, a minor's parents, who might have a whole slew of other motives.
The guardian ad litem is appointed by a court to be a neutral party whose only responsibility is to protect the interest of the child. The fact that this suit was filed against the estate by a court-appointed attorney leaves me feeling pretty sure there is good evidence as an attorney appointed by the court would be in some serious trouble (along with having no motive) if they filed such a claim without having evidence.
A civil lawsuit against a Greer woman's estate and her fiancé accuses them of assault and battery, intentional infliction of emotional distress, more.
www.greenvilleonline.com
ETA - to address
@evilwise, there may be enough evidence for a civil trial (preponderance of the evidence) but not enough for a criminal case (beyond a reasonable doubt). Agreed, messy, messy.