Heroin Addict Symptoms?

Hello everyone. My roommate/friend that confessed to me about she was a heroin addict. She was using methadone for a while but decided it was harder to get off of that stuff than the heroin. She started using the heroin again. She just recently was admitted into a 10 day clinic for substance abuse to go through withdrawl. She came back and he was looking better than ever. She was alive and talkative. The most noticable thing was that her eyes seemed normal not tiny and unchanging. Lately she has been withdrawing into another room, spends at least an hour in the bathroom when she says she has to go, or staying outside for half an hour to smoke, she has some trouble falling asleep but when she does it is almost impossible to get her to wake up, sometimes she falls asleep on the couch and I can see her twitching,sometimes she goes out to her buddies (who either are users or have used before) place and gets home at strange hours. I am worried because she has a great job and I think that she may be risking her job if she is still using. I confronted her about it but she just gets mad and says that she isn’t using. Can I believe her? I just don’t know anymore. I feel that she is never going to get better and that I should just give up on this friendship.

methadone addiction