How were these two integrated in the first place?
How long was it and what do you remember about it?

Can you tell who is the aggressor?

Really, the only thing that might work would be a complete, and slow reintegration.
Then later,(using a large playpen-cage) Use vanilla on the tails, to make them smell like each other and feed them close to each other (one in cage) etc. This will take a couple months.

It is very difficult to break the mental 'photograph' that these two have taken of each other when they met, but sometimes it can be done.