Your girls may indeed be happier with having each their own territory with a divider for interaction and mutual stimulation. I find that it helps to have adjoining hay corners that are open to the other cage so they can sleep next to each other in the hay if they like.
Contrary to what is making the rounds online, piggies don't groom each other mutually all the time, don't sleep snuggled up and don't share hides. But if they don't like each other and there is a constant dominance issue, then it is better to call it quits.
You have given your girls all possible chances to have their say in how they feel about their relationship, so please don't feel guilty or like a failure. Nobody can make piggies like each other; as little as small human kids. They are very much their own complex personalities. I have certainly my own fair share of sows (not rarely actually sisters) not getting on and carrying life-long grudges what would come up again and again with each attempt, and rather grow than settle down.
Although my worst pair of squabbling sister (from a horrible background with not enough milk from the mum) did move in together after years apart a few weeks before their death when the despised sister was the very last piggy they would accept; but by then they were nearly 7 years old and valued companionship over power struggles...
