For the ones that have 99% affection I use a Nazuna Cake to get them to 100% and get a flower gem. I then sell it for bond crystals leaving me with the 0% affection one. I dont really use event girls anyway (except for some like adenium rainbow rose and lilly of the valley?) so id rather get stuck with the 0% affection ones to then get another flower gem if I decide on maxing their affection