I have no clue technically. Never made anyone BFF either, so I wouldn't know how that affects he pink bar. But I'm pretty sure that just deleting their marriage will do nothing more than give them the status as single. If chemestry is super duper they will sill build romantic relation faster. If they were BFF I assume they still have that status. Hm, did you check if they have a BFF trait? If they do, you could delete it, but I'm not sure why you would do that? Also, if you want to totally reset their relation, and they don't have any family tree involving parents etc, you could always take one o them via the album, then to CAS as to create a new sim, and they will never ever have met before.
Lots of fuzz for a not played old save though.
I do the "save as" thing, too :) But only for back up, and only 2-3 times during a RL year.
