I have a hopeful, and probably naive, view that Bella and Jill will be a do-over of Melissa and Megan in AL. The situation seems somewhat similar where we have two close friends who are interested in the same guy; one who's very sweet and innocent, and the other who's more emotionally closed off but capable of deep affection.
Perhaps these two will have a threesome/sharing path with the MC because, again, much like in AL, the MC is really bringing Bella out of her shell and making her happy, so I could see Jill being very encouraging of this since Bella is her best friend and she will no doubt want what's best for her, just like Megan did for Melissa in AL. I also think that Jill could be OK with such a sharing-type relationship because she's a people-pleaser, and whilst it would be an unconventional relationship, all parties involved would be happy to have each other and I can't see there being any feelings of jealousy among them either.