@Kuyu
for one, they aren't celebrating a complete victory, but they DID successfully repel the invasion and defeated an S rank monster, so at the very least they get to celebrate saving the village today, and possibly the locals are also celebrating learning their friend's daughter lived and is doing well?
for two, Mel's specifically the goddess of reincarnation. yes, she's a god, but only a single god out of many (we haven't met others, but she's got a pretty specific dominion, so there HAVE to be more covering all the other stuff), it's not like she's all powerful or all knowing at the best of times, especially not now since she's bound herself to a limited form to allow MC to summon her since he doesn't have the mana reserves to summon her in her true form. as for why she doesn't punish Clive...that depends on the rules of the world, it's possible, probable even, that she can only prep them to reincarnate, maybe give them a "divine oracle" (aka mission), and send them on their way, but once they arrive in the world she is no longer allowed to interfere. that's a pretty common world setting, and if that is the case, the help she's given MC would be an exception to the rule, most likely possible only because of him asking her to become his summon(/wife?) ...also if that is the case then while she might be able to watch Clive's actions (and probably disapprove) she wouldn't have right to punish him OR to spy on the other humans around him and learn that they were planning a human on human war for dominance over the continent since, as far as we know, the rest of them are NOT reincarnated ...also no spoilers, but there's a little line she drops two chapters from now specifically regarding clive that also has interesting possibilities tied to it