When you approached Leandra, there should have been a dialogue started, and combat starts as soon as that is over. As long as Leandra is friendly, you are not going to be able to get the wand you need to continue.
Do you have a recent save you can reload, and go through the section just before then again?
You can try attacking her, or casting an area effect spell nearby, but if she is waiting to start a dialogue, she may be invulnerable.
If reloading doesn't help, please email supportdos@larian.com, with a brief description and the report.zip file (or a Dropbox or Google drive link, etc) generated by the D:OS EE Analysis Tool (for Windows). Extract the zip file somewhere and run the AnalysisTool.exe. When that loads, browse to the install folder (if it is not automatically detected), optionally run the tests first, and then generate a report (it will be saved in the same location as the Analysis Tool).
The report will contain system and game information, as well as your saved games. To reduce the file size, you can delete most of the saves from the zip; leave your latest, and, if available, one after or near the end of the fight with the Trife.
