What would you have done to her when you were growing up?

OK, maybe hitting her or tattling to Mom wouldn't be appropriate...
Seriously, I'd ask her to take them down with the explanation that you still own the copyright and that you're afraid that someone on Facebook will take them and use them without permission. Then there's the fact that Facebook has tried in the past to update their terms of use agreement to include language that gives them rights to all photographs uploaded on their site. I think they backed off on that but I wouldn't be surprised to see them slip that in again.
If you're not comfortable doing that, perhaps sending her some low resolution copies with a watermark so they can't be picked up off of Facebook and used elswhere would be an option.
I also wouldn't do any more business with her or give her or her husband any pictures besides family snapshots unless they're watermarked.