Try to be understanding about her parents.

They haven’t necessarily turned against you (although I admit I don’t know all the details). They likely believe they are doing everything they can to help and support their daughter. Instead, they’re likely enabling her whereas you’ve drawn a hard line and set firm boundaries and expectations. That’s good. Keep doing that.

You said your wife is probably an addict. That sucks. She’s not likely to commit to any kind rehab (outpatient or inpatient) unless she either feels like it was her decision to do so or she hits rock bottom. Often, and unfortunately, both of those scenarios happen simultaneously. She’s not likely to get there as long as she’s got loved ones who are willing to enable her and reluctant to set firm boundaries and expectations.

Email me if you would like the contact information for an intervention specialist (he’s also a recovering addict). He can call her parents and let her know the reality of what their daughter is doing and how they should deal with it. Meth is bad shit. Worse than alcohol or even cocaine. If she’s hooked on meth, she needs to get to rehab ASAP so that they can help her with medical treatment first and psych treatment in the long-term to work on recovery.