I'm going to stretch it a little bit and include Elaine in the comparison.
the problem with Elaine is the trust we have no reason to place in her, but her behavior toward MC is positive from the beginning (certainly taking into account the deception Bella enacts). but on balance she keeps every promise she makes to us. a pity that the real story of the relationship with young Mc will only be known by those who have a romantic relationship with Elaine.
in contrast with Jolina and Bella the problem is trust, which they both betray but with quite different dynamics
the problem with Bella is not that she is the gold digger, and that she has been Donald's mistress. the problem with Bella is that seemingly every action she takes toward Mc has a specific purpose, that of pulling him and Elaine away from their share of the inheritance, and to do this she sets no limits on herself, pretending to help MC, and doing everything she can to make him feel guilty about it, all she does is manipulate him into hating her sister. and it also becomes hard to believe her when it comes to physical attraction, is that real or is that part of her plan as well? here the developers really have to pull a rabbit out of the hat to make her version acceptable.
about Jolina the betrayal is less pronounced, first of all because at least initially she does not know MC and so it makes sense that she would want to help her old love anyway, as opposed to a stranger. the further we go, however, the more substantial the betrayal becomes. Jolina recognizes Elaine's photo just before she accepts MC's offer to host her at the beach house, even then does it make sense for her to keep holding up the game to Bella? but then especially the next morning the developers couldn't resist the cliché of "I have to tell you something, it's urgent that you know, but not now, later," and this later never comes, which makes enough sense if Bella is also a guest at the beach house, but otherwise, all of Jolina's thanks ring really false. but between Bella and Jolina there still remains a difference that at least for me is decisive: Jolina shows repentance, she knows that she is in the wrong and that this could cost her friendship or even MC's love, whereas Bella like a bulldozer continues in her scheming with some slightest hesitation.
