@EbonyRaven96 Yeah. I've seen stuff like that happen before. The only thing I was ever able to surmise is that there is a hidden trait or something that causes two sims to have a harder or easier time of getting along.
I've been playing these games for years. Since Sims 1 days. I have this thing about relationships in the game. I want to do them like all the time. Test them, see what I can do with it. Different sims, combination of relationships...etc.
Some sims just have a harder time than others creating relationships. Sometimes two sims will just naturally flow, I barely have to do anything. Sometimes it's like you've seen. Everything they say just results in unpleasantness.
If the sim is always in a Sad mood, you can try playing as that sim for a minute and see what's the cause of it and how long it's going to last. Death of friends last the longest I think. 2-3 days at least.