What is the ruling on removing the lawful hijab in a non-Muslim country if wearing it leads to the risk of spreading news of one's presence and fear of thieves?

If what is meant by hijab is covering the face, then the preponderant opinion is that it is obligatory. However, there is no harm in uncovering it in a situation like the one mentioned. As for if what is meant is covering the rest of the body, then covering it is obligatory by the consensus of jurists, and it is not permissible to uncover it except out of necessity. What you mentioned is not considered a necessity. It is possible to look for another place to meet the mother, or to use other means of communication such as the telephone.