The safety of supplements is difficult to determine. There is rarely any data to support the use of supplements or their safety, particularly in people with specific health issues. It is also critical to know the full details of each patient's medical history and other medications and supplements. Given your friend's history of liver issues, I encourage them to make an appointment with a hepatologist (liver specialist) to determine whether this is safe.
According to its label, Green Vibrance contains various dried weeds. It is important to know that supplements are not subject to the same FDA scrutiny as prescription medications. A recent study showed that many supplements do not actually contain the substances they claim to contain. Additionally, there have been many high profile cases of supplements being removed from the market because they have caused liver failure and death. Many natural herbs and plants are known to cause liver damage. In fact, some are so deadly that they can cause complete liver failure and death. Without knowing the full details of your friend's liver issues, I cannot comment on the safety of this product. As such, it is not safe to take this supplement without first consulting a liver specialist.