Absolutely. It's an attrocity, but at the same time, I'm not sure I'd know what to do about it. In a society not equipped to handle this, I fear they might simply lock up the "owner" and set the slave free, but that's unlikely to do the slave much good in extreme cases like this.

Setting them free is great for people who have family that can take them in, as is often the the case when the slavery lasted a couple of months or years at most (which is probably the case with adolescent girls pressured into prostitution, for example). But in cases like in the article, where someone has groomed to be a slave from a young age, and has lived that life for decades, been moved to another country even; the family that owns them may be all they have. You've got to free them, but that might take away the only thing they still have, and sever the connection with the only people they know and care about.

It's a seriously fucked up situation.

But yes, when you know someone who seems to have a slave, that is absolutely something to confront them about.