There's nothing inherently dangerous with combining Methamphetamine with a reasonable amount of Chlordiazepoxide (Librium) or any other Benzodiazepine.
I believe most people would save the Benzodiazepine for when the Methamphetamine wears off. It's a good way to avoid the anxiety/depression that often is at the tail end of a high-dose Amphetamine experience. Others would take the Benzodiazepine simultaneously as it would smooth the jagged edges of the Amphetamine experience, relaxing you, reducing tics, that sort of thing.
At any rate, this isn't a dangerous situation in any way that I'm aware of. Let me know if you have any other questions.