I want to donate half my liver to my fiance, what factors are considered? Where are these procedures performed?

Your Health & Desire. Living donor liver transplantation can be performed safely at unos-certified liver transplant centers. The center will examine you from head to toe to make sure that you are motivated, aware of the risks, and healthy enough to donate and live a normal life after your operation.
Much info needed. For a living person, the donation of a portion of the liver for transplantation into someone else is a major operation and should be undertaken very thoughtfully, both by the transplant team and by the donor (that is you!). These are very complex operations that are only done at specific centers in the USA (go to unos.org) to find them. It is a big deal - and could make a big diff. in both lives.