Hello SJ--Welcome to SR! Glad you found us....
First, I really think your gf should be the one to ask her father for help. It is hard to do, but it really is better for the addict to be the one asking. Second, what are you doing for you? Addiction affects not only the addict (alcoholic), but also everyone who loves her. You might want to check out our Friends and Family of Alcoholics forum. There will be many people there who can relate to what you are going through and will be able to give you more specific advice.
In the meantime, hang in there!