Hello Papagarv1,
Welcome. Sorry I am late in responding to your question. You've asked for no judgement - you won't get that from me. Very sadly ppl in chronic pain have been driven to all kinds sources to treat it. I don't condone buying opiates off the street, especially such a complex med like Methadone. Her risks are very very high! Please do your research. My concern is for her physical safety. Now I'll shut up and answer your question.
Pregabalin, is a medication used to treat epilepsy, neuropathic pain, fibromyalgia, and generalized anxiety disorders. It is better known as Lyrica. Many physicians order opiates and Lyrica together. Methadone is a different animal. I'm not confident in saying you can safely take the two together. Your best source would be a Pharmacist. They are the true experts in medications, the side effects, interactions and so forth. They are free and you don't always have to give your name.
Good luck - and be safe!
~Tuck