Self-destructive or not polygraphs aren't really a good way to see if someone, especially a stressed someone is telling the truth. They can easily be manipulated to provide the desired result and if she's addicted to medication that could cause great stress. Don't consider polygraphs to be the "great lie detector" because they aren't, they just measure how stressed you are for the most part. Watch the Penn & Teller show on polygraphs, it's pretty close to the truth.
Take care of yourself and your family and make sure she has good legal representation.
