I'll offload it before it gets to crazy, I would of thought at 5" it would of started to show its true personality, my Texas, Flowerhorn and green Terror have no problems doing so!
I can understand it in baby fish, but usually by sub adult the 'true' side comes out.
Bifa's arn't some crazy rouge fish that indefinatly will destroy anything in its way. I'd consider them about the same temperment as blackbelts, Which can be good or bad in tanks depending on the stocking. Smaller and conspecific fish(similair traits) they tend to destroy, but they back down from fights easily.
And it even seems like you have a prettly relaxed one. It may even be female. Dont let somebody elses unsuccessful stocking scare you away from Vieja/ Paratheraps.