@iainandchrista- Good morning and welcome to Connect. I am a volunteer mentor for Mayo Connect and am mostly on the the Lung Cancer Group. Finding out that you have metastatic lung cancer is a shock and life changing all at once. I am also a CBD user. I have not had immunotherapy but have done a lot of research, as @artscaping has stated. CBD oil, cannabis and Chinese herbs have not been clinically tested to see if they are compatible with immunotherapy, at least not in any regulated way. It is only my opinion though that her oncologist be made aware of any and all medications other than what has been prescribed for her so that she can get the most benefit from any treatments she might be offered. Has she told her Oncologist as yet?