The Copenhagen Interpretation is that both types of flowers exist in operator space, satisfying a generalized time dependent wave equation which I'd put here for you if I could show integral signs and greek letters and bra-ket notation. When Katrina made an observation of the flowers, she constituted an operator acting on the superposed wavefunctions, causing the wavefunction to collapse as its rose manifestation.

The Many Worlds Interpretation holds that the flower function exists in many parallel universes, manifesting in each as a slightly different wavefunction (flower). In our universe the flowers manifested as roses. In a parallel universe an analog of Katrina received other flowers.