I am so sorry to hear about your dog being exposed to crystal meth. My name is Rebecca. I am a veterinarian and will do my best to help.
How valium did you give her?
What is she doing: trembling, shaking, confused, weak? If you check her gums, are they pink in color?
How long ago would she have gotten the meth?
There is no antidote for meth, over the counter or otherwise. We just do "supportive care" such as IV fluids, and drugs for the muscle tremors and excitement, until the drug wears off. We use a tranquilizer called "ace" or acepromazine for the tremors, but unless you have access to some, you can't get it over the counter. All you can do is try to keep her quiet, in a dark quiet room, and wait out the symptoms and hope they don't get too bad.
Let me know how she is doing and what other questions you have.