I have legal guardienship of my nephew through the court. Mother is a drug addict and did not show for court. She now says she is clean, pregnant again no job or stable home . She lives in another state so only calls once a week. She says she is taking me back to court should I be worried?

You should be prepared and cautious, that's all you can do.
We can't know what she is able to prove or convince a court of.
Some will depend on what states are involved.
Courts more and more try to have bio parents be able to spend at least some time with their children. I know she's in another state, but how far away?
Have you told the boy about her? How old is he?

He is 4. He has been with us for a year and a hlaf. He does know his mother. She lives 8 hours away, and only visited once when I paid for it. She is always invited, but has no money.

Courts often want and try to get the child back into the home with the parent, so I agree, careful at this point. With no job and no money, not sure how she would pay for court and attorneys, But yes she can try and if the drug use was the reason she lost the child, they may look for a plan to return the child if she is clean.