Well, let's review Miss All Sunday's actions and motivations for a moment, shall we? She helped Croc with his plan at every step, knowing full well that it would cause the deaths of a million or more people. And, she had made preparations to kill him after they located the Ponyglyph. The latter would have the effect of keeping him from disposing of her after she outlived her usefulness; in retrospect, though, it might also have been some effort on her part to ensure that Croc never got the chance to do to any other island what the World Gov't. did to Ohara. During Sanji's infiltration of Rain Dinners, she saw him heading into the building, while everyone else was headed out. Yet, despite noting this suspicious behavior, she did not immediately report it to Crocodile, instead allowing him to continue pursuing Chopper. She tricked Pell into attacking her head on by making it look like she had run Vivi through. She could have crippled him for several weeks with more effort, but didn't. She blew up the boat Igaram was on, but didn't confirm his death afterwards. Those were her actions. What was her motivation? To see if the Ponyglyph hidden in Alabasta contained the True History, as well as shielding herself from the World Gov't. in the interim behind the mantle of Croc's status.
Her actions as Miss All Sunday were criminal, self-centered, and reprehensible, but they were not irreversible evils, nor were they done with any deep-seated malice. Or at least not with the same sense of malice that Croc displayed. Moreover, had her attempt to kill Croc succeeded, she would have lost the protection his Shichibukai status afforded her. She would have been back to living on the run, with no one to turn to, and little hope that anyone would listen to her account of the facts or the True History. But since she had given up on life anyway, maybe that wasn't such a big concern to her anymore.
As for Robin and Vivi meeting again face to face, I think they would be very uncomfortable around each other. Robin tries very hard, it seems, to live life as a pirate i.e. without regrets. Seeing somone she knows she has wronged would no doubt cause her some pangs of guilt.
EDIT: Or, she might genuinely apologize to Vivi, be forgiven, and move on to that Hot Lesbian Action Local mentioned.