Number one, if you talk to her about it, don't put it that way! Saying she's a bad parent isn't going to get you far.
Now, the real issue. Whether meds are appropriate for her children or not is not something a stranger could tell you. What I do know is that they need to be used together with various behavioral and educational techniques to help the kids figure things out. Also, they need to be administered under the supervision of a physician. If the kids are, you think, really in trouble, ie not eating or sleeping due to too much medication, or in some other form of imminent danger, then it might be appropriate to say something.
But, ultimately, they are her children. You can help as much as she will let you, but you can't raise them for her.