Well, I don't really see Diana killing anybody for sleeping with the wrong woman, or, like, setting a perfectly innocent person on fire just to hurt somebody who hasn't, actually, wronged Pele and is in fact doing her a tremendous favor at that very moment, no matter what the alternative is. Pele is Zeus and Hera combined in terms of mythological shenanigans - she does the seducing and the petty vengeance, all in one convenient fiery package - so there's every possibility that being her champion would lead to exactly the same sort of moral quandary Diana just faced with Zeus. (Unless, of course, Pele gets a white hat facelift like most of the Olympians did, in order to protect Diana from just that sort of problem.)
Hard to say the extent of her pledge, though, anyway - the whole "I made a terrible promise and then it was okay to leave" suggests a one-time exchange, some form of divine reparation (kill Zeus, maybe, which would make sense from Pele and could fit Diana's attitude (and could explain the upcoming "Diana in Themysciran jail" solicit)), but Diana's actual conversation with Pele seems to indicate Pele has inherited her obligation to/championship of Kane and her service is more long-term, a total offer of fealty. I guess we'll see.
Anyway, I mock, but this actually sits much better with me than the conversion to Milohai. Her obligation here is pretty concrete and indisputable, and neither party is pretending the relationship is anything other than it is. And this actually is her responsibility, instead of its direct opposite like last time. To carry the metaphor to its tortured conclusion, if she whored her faith out to Kane, service to Pele after Kane's death is choosing to raise and care for the subsequent baby. It doesn't relieve or redeem her betrayal of Athena and the other Patrons (the... cuckolded spouse, in this case? Why do these metaphors always get away from me?), in fact, it's only likely to make that relationship worse, but it's still an appropriate response, and the only right one for Diana.
damnit, I swear I know how to spell, and what's this parentheticals inside my parentheticals stuff again, man, this is just not my week for coherence at all