I don't think it's nepotism as much as brand name recognition amongst running circles. Ritzenhein is a brand. Keflezghi is a brand. Goucher is a brand. Brands sell shoes. Go to any of Addison's meets and the announcers introduce her as Ritzhenien's daughter -- hell even Flotrack commentators do that. That is the weight of the situation.
If ON was truly seeking top female HS talent to sign, it wouldn't be Addison as first choice. If her dad and ON were objectively looking at the best distance runners even in Addison's own grade, he would have told ON to sign Elizabeth Leachman.
Elizabeth, in the same grade as Addison, has run a 15:25 5000m and has faster PRs across the board. All this while doing Parker Valby-style training (ton of cross training because of past injury issues). Any knowledgeable running fan would realize the ceiling of Elizabeth is so much higher than Addison's without the privileges afforded to Addison with a fraction of the public pressure to perform.