Consider it an honour to help your friend during this painful time. And then, get organised. Develop a list of questions that you will need your friend to answer. Does she want the service in a certain place of worship? Is there particular member of the clergy she has in mind for performing the service? Does she want a private or open service? Who else would she like to have involved to do Scripture readings and serve as ushers? Would she like to have a reception somewhere for some or all of the attendees of the memorial service? Decide upon the best way to get the word out to friends and relatives about the service. Elicit help with phone calls and preparation of a newspaper announcement.
Then get to work to put her plans and ideas into reality. Visit, or at least speak with, the clergy person. Ask for his/her input and checklist of what needs to be decided and completed. Keep your friend informed and get her feedback. By merely being there, listening and taking care of the details, you'll undoubtedly be a great help to her during this trying time.