I haven't seen the part in a while, did Edea actually get powers twice, or did she just get them once from Ultimecia when she was 5?
She actually got them twice - once when she was five from a sorceress of unknown origins, then later when she was Matron of the orphanage during Squall's stay there. Squall was probably around 4 or 5, so Edea recieved Ulty's powers about 12 years before the game begins. We discover this at the end of the game, when the adult Squall travels back in time to see Ulty transfer her powers to Edea. Edea is clearly an adult, and Squall sees a younger version of himself. This conflicts with Edea's claim that she first recieved the sorceress powers at age 5, so she must have gotten 2 sets of powers.