Did it really though? Sei has always been a great help, so the fact that you need her despite snubbing her hasn't changed all that much. The prince is still a jackass focused on the other girl, who is still quite valuable in terms of potential. Heck, I'm pretty sure it's clear at this point that Sei doesn't want to be known as the Saintess either anyway. It's basically an open secret.
So really, what's changed?
@Akabane It's not a matter of courage, it's a matter of being yamato nadeshiko. She's basically super satisfied being controlled by all those handsome men and working for them for little reward.