iirc it was never mentioned that Bella is friends with Jade and Burke, so i believe that line about student and friend was solely about mc. Also, they mention how they tried to involve her into their sexual life but she rejected that offer because "she was already in love". Also, Burke said that.
Obviously, if there was something between these three, Jade would have known that and that Burke's line would be absolutely pointless. And because all of that i can safely say that there was nothing sexual between them.
You know, maybe Bella dislikes Jade because her husband cheated on her with Jade, but i personally doubt that. Maybe she dislikes Jade just for whatever reason.
Bella's inner monologue in the pool implies that her husband cheated on her.
So imagine, the love of her life betrayed her, of course, such a situation would affect her behaviour and overall opinion about men.
So yeah i think it was all her husband fault, fuck him(not literally).