The reaction pp → ppη → ppγe + e − is discussed within a covariant effective meson-nucleon theory. The model is adjusted to data of the subreaction pp → ppη. Our focus is on di-electrons from Dalitz decays of η mesons, η → γγ * → γe + e − , and the role of the corresponding transition form factor F ηγγ * . Numerical results are presented for the intermediate energy kinematics of HADES experiments.