Just to double-check... they're both spayed, correct?
If not, they can't truly be considered bonded and their hormones can provoke vicious or even deadly fights, so they would definitely need to be separated and kept apart until about a month after their spays (takes that long for hormones to die down), then re-bonded.
If they are... my girls have never gotten into a bad enough fight to actually result in an injury, but their bond HAS broken a couple times. If they're both spayed yet they're fighting that badly, then something has obviously upset their bond - I would try taking them to neutral territory (somewhere that neither girl has ever been before) and letting them have a supervised play-date there (like you would do if bonding two adult rabbits for the first time). With my girls, that was enough to fix things both times - the first time, I set them up in an x-pen in my neighbor's kitchen and the second time, we used an x-pen in the front yard. The neutral territory is a bit of a reboot for them, it seems. The first time was during recovery from their spays, so they did actually live separately in adjacent recovery enclosures; the second time I went right for the neutral territory trick and never had to separate them at all.
If you can't mend their bond with just some time on neutral territory, then I would separate them where they can still see/smell each other but not fight through bars and continue to try a play-date on neutral territory once or twice a day. If that doesn't work, you'll need to separate them *completely* (different rooms and everything) for 3-4 weeks - this essentially resets things completely and you'll have to bond them again from scratch. If you have to resort to that, then it's best if neither girl stays in the territory they normally share... otherwise you'll have to do a really thorough job of cleaning/deodorizing the entire area to make it neutral again (so that the girl who was allowed to stay there doesn't now claim it as "hers").