Assalamu alaikum, I can't tell her what to do but I will tell you waht I would do..
I understnad she is married for 3 years, and she probably really loves her husband, but the husband is taking drugs, and if you take drugs ur more then likely not caring about your islam at all..
Allah prohibits making salah will intoxicated off drug/alchohal
Anyways if the wife can, then she should consult him tell him she knows whats going on, and try to help him for the sake of Allah , and may Allah reward her for doing so.. Give him some time and additional help.
If he says "I don't have a problem" and continues doing so, threaten to leave him and if he hits her or does anything which a drug addict usually would do, then she should run away as fast as possible..
You know I understand many women say we can't leave or what ever , life is too hard.. Women need to understand something and so do we brothers.. There is always a rope of Allah somewhere , we are just blind to see it at some points.. What I am trying to say is, there is always a way out of situations, ALWAYS.
Allah subhanahu wa ta'ala mentioned in the Quran "We only place on souls calamaties due to their capacity."
If this women truely fears Allah, and wants the akhira more then she wants the dunya, she will leave consult with the masjid get a new husband eventually inshallah, and keep her mind focused on the hereafter...
If the dunya is too much of a concern for her then honestly I don't know what to say but what I said at the beggening, because this life is a prison for a mui'meen, and paradise for the disbeliever...
Rassoolullahi (salla allahu alayhis wa salama) said, "live in this dunya like a traveller"
and Allahu aleeem , allaho akbar
Assalamu alaikum, wa rahmatullahi wa barakatoh.