Something I appreciate about this guy is how he isn't judgmental in the slightest. He hates the effects of war, but he understands that there is motive behind each action. It may not be pleasant, but all such things are a part of life. That's a sign of wisdom, right there.
She did act that way during the bowling chapter, so it seems like that version of her is still here, it's just buried under all the pent up...stress. I expect we'll see more of that side of her as she gets more comfortable around him.
Look, I get wanting to spare people, but this guy gleefully boasts about eating countless people to fuel his power as a demon. This one's a pretty cut and dry case of exterminate and move on.
Honestly, if one of her main goals is to husband up her brother, avoiding showbiz is the right call. Can you imagine what the tabloids would say about that relationship?
"Is this Sato guy actually okay?"
Don't worry, he's a Grade A certified Japanese-model Herbivore Male Protagonist. She'll be fine because nothing will happen.
Ever.
It may be a rivalry, but if you look at the two pictures, Cynthia is pretty uncomfortable with Allen, but is quite happy with Weiss. Therefore, I declare Weiss to be the better hypothetical NTR scumbag. A coveted title, to be sure.