On the one hand, the course of time is not to be meddled with, the laws of the world are not to be modified. They all agreed on that, when Caius described his plans, when he threatened to rewrite history to erase his own mistakes. If Minfilia will someday become this Hydaelyn, there is little Cecil can do about it.

On the other hand...

"Choices change. No destiny is set in stone until it has occurred, and destinies born from distress lead to darkness and ruin. If what she needs at the moment is respite, it is in your best interest to let this world grant it to her."

If this is a rare case of a divine being that cannot understand mortal needs and refuses to learn, well. He'll simply have to be persuasive.