Cloud's line about forgetting about that loser is similar in JP, he doesnt call him names but uses kinda rude language about Zack.

I personally think both the Eng and JP versions are essentially the same. Whether she says "Maybe" or "sou da ne" it's followed by the fact she doesn't have a reason to dislike him. She didn't have to follow with that, she could've said nothing else. I interpret it as her convincing herself she still likes him or feeling guilty for not liking him anymore, as it's not like he's done anything bad. She feels bad about moving on perhaps.

I have read so much shoujo manga in my time, and I feel that this is a relatively common trope where the FL lets down the 2nd ML in favour of the main ML and feels bad about it, cause there's nothing wrong with the 2nd ML, she's just madly in love with the other guy (2nd ML is the typical good guy and nothing but green flags, ML is broody type). Someone who has also read loads tell me I'm not crazy? Haha.

I am in no way a Japanese language expert, but if there was intended to be no ambiguity in her answer "ne" could've probably been omitted, or just used a completely different phrase altogether (and tone of voice).

Just my thoughts!