So I'm assuming the Head Nun lady, who just so happens to have the same last name as the FMC and her sisters (I'm sure that's not plot relevant or anything), put the Priest guy up to this to try and get her "definitely not her daughters" to give up on the whole Temple thing. The question now is whY?
So just seeing a hard-on makes Mia go into succubus mode? How did she survive until now? Has she actually succeeded in her goal of getting 100 sex partners?