(That's not meant to be a potshot against Tharja, by the way; she's just the first example of another obsessive character that came to mind.)

LOL, Tharja was the first comparison point I had, too, so its okay. Yeah, Monica remembering all the times she had tea with Edelgard is (imo) more in line with Eliwood remembering the number of wins, losses, and draws in his monthly spars with Hector. She's obsessive, but the things she obsessively remembers are innocuous.

People twisting characters into hating whoever they themselves hate feels like childish playground bullshit to me.

Childish playground bullshit AND typical teenage Mean Girl shit. Or petty office gossip between adults who really should know better.