Rehab, relapse and recovery

You are a positive force already just by voicing your concern.  I think that it is a wise decision for your girlfriend to NOT move back with her mother who, from your question, is not a good influence.  I agree, also, that moving someplace new is a stressor as well.  That said, your girlfriend needs to look at her goals, and her willingness to achieve her goals. When you say "move up" does that mean to be closer to you?  If so, you can be most supportive and an ongoing positive force by talking openly and honestly about your own concerns, feelings and needs, as well as your hopes for your girlfriend.  She absolutely will need an "after care" plan from the rehab center which ought to include attending meetings ~ Narcotics Anonymous (NA) and if you are both truly committed to this relationship then I would strongly recommend that you attend some Nar-Anon meetings (for family members of those who are addicted).  Additionally, your girlfriend needs ongoing counseling where she can honestly deal with what brought her to need drugs. The purpose of addictions is to keep us away from our feelings that seem too scary or overwhelming to deal with.  Your girlfriend started taking pills for a reason, and while rehab may have helped her to detox her system, it is only the beginning of her recovery.  There are a number of therapeutic interventions that can be helpful going forward, and I would ask her to discuss these options in depth with her counselors in rehab so that she can have a viable plan in place before she leaves the safety and security of rehab. 

I guess I have a number of questions as well that you will both need to address; like does she have a job... are her skills transferable to a new location so she would not feel forced to stay near her mother. Has her mother acknowledged the problem since your girlfriend entered rehab?  Does she have a solid enough income to live on her own or would the 2 of you plan to live together, would she need a roommate, etc.?  IF you plan to live together, then I strongly recommend couples' counseling for both of you so that your communication can be clear, healthy, compassionate and respectful going forward and you'll learn more skills in dealing with the issues that come up in life and in relationships.

Look into the following counseling options going forward and discuss them with your girlfriend: Insight oriented counseling to look at the source of her discomfort and get to the root of the problem.  This can be done through talk, hypnotherapy, EFT (emotional freedom technique) mindfulness based therapy, and work with a therapist who has a specialty in dealing with addictions. (it doesn't necessarily have to be drug addiction specialty).

Neurofeedback can also prove to be helpful in abating the urges for one's addiction. This works especially well as an adjunct to talk therapy.

Should your girlfriend need to look at changing jobs or careers, so that she has greater freedom to change where she lives, she can look into vocational counseling through the state as job training and schooling might be a great benefit she can receive. 

Self-help books can also be beneficial, if she is willing to do healing work on her own in addition to the support and guidance she needs to live a more empowered and fulfilled life.  I recommend books by Louise Hay, Wayne Dyer, and Don Miguel Ruiz.  My book Being Well Within: From Distressed to De-Stressed, is also a helpful resource in dealing with life's stresses. 

While you have a lot to deal with and think about going forward, I am sure that with open and direct communication you will be able to make healthy and respectful decisions for yourself and allow your girlfriend to do the same.  It will all ultimately come down to trust: your willingness to trust in your own abilities to cope with this new situation in your life and trust in knowing that you need to take good care of yourself which will then communicate to your girlfriend that she needs to do the same for herself.  I wish you the best.  Please contact me should you have any additional questions.