not sure what to give for advice, but I can say to be careful of a few things...
If you, lets say, kill off one of the plants, or if you try to separate them, it is likely that you will have roots break off or get left behind. A lot of the roots at this point will be tangled together.
The problem with that is the left over roots will decay. And when they decay, you will have a chemical reaction that can cause the ph to spike after a week or so. I have had similar situations with decaying roots due to one thing or another in past experiences. And the ph spike was enough that it upset the plants.
If I had to give a suggestion, I would say to leave both plants and strategically prune the plants so branches do not cross, think of each plant as being one half of the whole (side by side, yin and yang if you will).
Also, if you do cut one down, just be sure to do water changes for a few weeks and monitor the ph and im sure youll be fine.