Not sure what the tattoo has to do with your concern.
And getting into a car "willingly", or appearing to, doesn't determine that a person isn't acting out of fear, or under threat of harm, depending on the situation.
Other than that, she's a legal minor who was considered to be in "grave or immediate danger" for whatever reason. It doesn't seem to be the typical case but I don't know that it falls outside of what the system was intended for.
Knowing more circumstances might paint a different picture, either way.