This belief that we have the power to cause someone else to relapse is poppy-****. It's part ego and part victim.
The only person who has control over addiction is the addict. It is common for those addicted to blame usage on someone, anyone or thing rather than take ownership for their own sobriety or as the case may be, addiction.
Remaining sober means learning and applying new skills necessary to cope with life as is, not as it should be.
Remaining sane when someone we love is in active addiction means learning and applying new skills necessary to cope with life as is, not as it should be.
I really like the way Jerect put it, you have nothing to lose or fear, at Alanon.