Harmony with 2 dogs in a home

Question
We adopted an 8 year old Wheaton Terrier approx. 1 month ago.  We already have a 7 year old Wheaton.  Both are spayed females.  It has been a long haul, but we are starting to see some harmony in the house.  In the beginning, Molly, the 'original' dog, was not accepting Casey the 'new' dog at all.  Molly is the dominant dog, although Casey has some dominance in her as well.  The major problem we have now is with one room - our family room where we spend a lot of time.  For some reason both of them go at each other the minute they are both in the room.  We have tried various methods to try and correct this problem, but with no success.  Molly will still 'go after' Casey occasionally in other parts of the house, but in these instances Casey shows submission.  It's odd, however, that she does not react this way in the family room and I fear that if we don't immediately separate them there will be quite a dog fight.  I would really appreciate your thoughts on this situation and some suggestions for how we can eliminate this problem.  I should also mention that during the night they both sleep on the bed, nose to nose, with no spats whatsoever.  Thank you in advance.

Answer
I recommend you make the family room the place where they are always under control-have specific spots for them, separate from each other, and they are to lay on those spots if not being asked to do something else.  It sounds like they are vying for control of the room, and if you maintain "top dog" status that should keep them from trying to decide amongst themselves.