I believe that Abigail still loves John Proctor; however, her conniving plots to get rid of Elizabeth got out of hand, and unfortunately, John ended up in jail too. And, stubborn John, he just refused to confess to witchcraft so that he could be released and live a happy, blissful life with her. So, John wastes away in jail, all because of Abby and her scheming. I am sure that she didn't want nor expect things to turn out that way. But once he was in jail, she couldn't do anything about it that wouldn't cast suspicion on her character. The adultery card had already been played, and anything she might do to try to save John would be seen as highly suspicious. Plus, by the time that John has been in jail for a while, the townspeople are starting to turn on Abby and her gang of accusers; too many people are in the jails, farms are going untended, children are orphaned. It's becoming pretty unpopular to be involved in the accusations anymore. Parris himself finds a knife shoved into his door one morning, a sure indication that the people are turning on the courts, and on Abby. So, she can't really do anything to get him out of jail.
In an additional scene that is occasionally put into the play, John meets with Abby in the forest to try to convince her to stop her nonsense and declare her accusation of Elizabeth a fraud. In this exchange, we see that Abby still cares for John, and imagines being his wife. She states,
"Oh John, I will make you such a wife when the world is white again!"
She is so deluded that she thinks John is "singing hallelujahs" that Elizabeth will hang, and then Abby claims, erroneously it turns out, that she will "save" him. She is clearly fantasizing about John, and she sees him as some sort of savior that opened her eyes to people's hypocrisy.
We get no clear indications of her feelings in the 3rd and 4th acts, but we can presume, from her desire to save John and be his wife, that Abby was incredibly dismayed at the unexpected turn of events at the end of act three, and as she skips town just before he is to be hanged, we can infer that she didn't want to stay around to see him die. All of her plans to be with him, by that time, had been foiled, and the town was turning against her. So, she bails. She failed in getting John, and whether she loves him or not (I believe she does), in the end, as usual, she does what is best for her and only her. I hope that those thoughts helped; good luck!