Hi,
Welcome to HCM and thanks for asking your question. I would like to know few more details from your side like what kind of immunity problem she is having and for how much time, is she taking any medications for that, etc.
Another thing i would like to tell you that
pregnancy is definitely possible and safe with low immunity, but with due precautions. She needs to have highly nutritious and healthy diet, avoid sexual intercourse, avoid long traveling, avoid heavy weight lifting, keep her private parts clean every time she is visiting toilet, take
folic acid tablets, take vitamin E/C tablets to increase immunity, avoid visiting places full of people, etc.
If you want to abort it,then also no need to worry, but you will have to take proper antibiotics and proper guidance of gynecologist.
Hope this will help you to clear your mind and you can come back to me anytime after having those information i asked you.
Best wishes and best of luck.