My best friend is a correctional officer at a medium security facility, she's dating an ex-con,help!?

My best friend of over 10 years now has recently started dating a new guy. Normally i don't try to be too judge-mental because she's a single mom with 3 kids so dating is tough for her. But recently she admitted she's started dating a guy who was just released from jail for crystal meth and that they are hitting it off. She claims he's really good with her kids and a sweet guy, (i'm thinking, yeah right). She admitted to me on the phone that she thinks shes suffering from depression and on the verge of a mental breakdown, i don't know what to do? She could lose her job just by someone at her work finding out she's ociating with this guy and she knows it but doesn't seem to care. 6 months ago her father got a DUI and she was so concerned about the backlash from that affecting her job and now she's dating an ex-con? I don't know how to handle this and whats more she kept it a secret from me and only her mom and a friend who is an ex-girlfriend of the guy knew about them dating. I am totally beside myself right now, she has said im her best friend in the world and likewise for me. I want to shake some sense into her but i don't know what to do or say. help!?!? I am also worried for her 3 kids they are still young and impressionable and an ex-felon is not what they need in their lives...