Girls usually don't fight (though I had one that did, but she had been freshly rescued from living with a rabbit for all her life, just to prove me wrong).
What you can expect is that they seem to "squabble" and "bully" a lot, which in reality is sorting out their relationship. The dominant girl will establish her priority and then try out how far she can push the other girl (until the undergirl draws a line). Being very dominant doesn't mean that they won't become best of friends afterwards, only what shape their relationship will take.
There will be rumbling and rumblestrutting like with the boys (she who rumbles last is top girl), you might get some low level chattering, quite a bit of headbutting/nipping with the undergirl protesting with loud squeals. Humping can happen; especially when one of the girls comes into season. Quite a lot of squealing and squeaking, if you have a drama queen.
How much and for how long you have it depends on how dominant your top girl is - it can take from just a few days to weeks. Top sow will stop whenever she is satisfied!
I'm wishing you the best of luck! Please don't interfere unless there are bloody, serious fights. It looks worse for the bystander, as piggies are not exactly subtle when they work out a hierarchy.