Today marks a week since I've been intoxicated

My roommate mentioned yesterday that I'm starting to be myself again. I had dreams last night with heroin laced imagery, making this morning a little uneasy :\
A couple days ago, I told one of my good friends that I was sick last week from drug use (I didn't tell her what I was using and she didn't ask) and that I'm detoxing, trying to sober up for good. She responded less than ideally. Brought up that this weekend a friend we haven't seen in years will be in town and he wants to smoke with us

I told her I don't want to, even though I'm very tempted. She kept up with the pressure, "oh come on! He's not in town often and who knows when we'll see him again? Just this one weekend!"
I've been through the whole, "one time, this is just a one time thing, I won't do it again after this," situation before. Many times. It never works out in my favor. I just go back to regular use after a while. What more can I tell her to get her to stop pushing it? She was supportive of my past decisions to sober up, but she's pushing it now because an old friend will be in town.
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And you're cutting off your head to spite your shoulders
Get behind the wheel, stay in front of the storm