OXFORD, Mich. — Reina St. Juliana looks at the photograph of her younger sister, Hana, and sees her beautiful face smiling back and her hands holding a bundle of lavender, one of the 14-year-old’s favorite flowers. Reina, 17, does not see how this photograph — part of a planned temporary memorial inside Oxford High School for Hana and three other victims of the Nov. 30 school massacre — could trigger trauma or why it should be placed in a school theater where most students won’t see it. For months, Reina and dozens of other students at Oxford High have battled with district and school board of…