Ren,
I think 15 minutes per day isn't bad especially if it something she loves. As long as she is happy and not complaining I would consider it a nice part of your daily routine.
I would worry about the chords though. I too have a 4 year old who started private piano lessons this year as well. He is only a little bit older than your daughter. I think there is no way he could play a 5 key span chord. Fortunately he was never asked to do so. Trying to do something which is impossible or extremely hard may ruin your DD's piano experience. It could be very frustrating for her. I would talk to the teacher and make sure he understands your point. Once her hands are bigger she will most likely fly through these kind of songs. I am sure there are other songs she can be taught before her hands catch up with her abilities. If she doesn't want to do the recital then don't do it.
