The younger one is naturally more aggressive probably with more drive than Vida had at the same age. They have hormones kicking in at about 7-11 months when they hit puberty having there first heat or males will start to lift there leg to pee, they can challenge you or any other lesser members of the pack human or animal at this time and again at about 1.5 to 2 years old when their adult hormones kick in to stop their bone growth and finish maturing into adulthood which may take another year or more for their full development. If they clearly understand the pecking order after these periods you should be good for the rest of there life until they get old some dog will get grumpier. Gaia will probably be the dominant one in the end but it can be achieved without a giant battle that could send both to the vet or worse, they can work it out slower after the pups are gone. The way they act at the door is because you haven't recognized that Gaia is dominant and should receive attention first then she wouldn't have to put Vida in her place for getting out of line also obedience should be very good no attention unless they sit or do something for you get also get into the habit of giving them less praise at the door coming or going making them sit when you come and go they won't get as worked up. When they eat or go outside does one wait or give the other one space? The settle exercise I described worked 8 months ago and things have been good till Gaia's second heat and also the pups are triggering the new battles if you do the exercise to the point that they will do it on command easily and figure out the pecking order of all your dogs and make them work for attention and give it to them in order, things should be good after the pups are gone if you keep on them in line. Gaia needs more work while Vida will stop fighting easier she respects you more and may have less rank or fight drive if they know 100% that any aggression will result in a time out on there side every time till they both give in to you together one will back down first and that will help them establish your rank and there own with each other. The problem will be gone if your consistent & work them separately till they are both very good then do it to both of them together giving them treats can make it easier to begin with but not together or every time. I have done this when a 9 month old rottweiler that had bitten the 3 & 10 year old kids he grew up with they play fought with him all the time despite my warnings. The 3 year old could later stand eye to eye with the male dog grab his face and roll him to the ground easily and sit on his head he lived another 9 years never a problem with the family again and was a very good guard dog. My 3 & 6 year old daughters can do it to my dog with alot of drive she has been doing the exercise with the kids for a long time they can do anything and the dog lets them they lean right against her give her hugs and she doesn't move she has been taught respect for them. I have done this with a dog that thought every dog was a rabbit didn't mater how big never tried to posture or dominate just had a taste for blood she could be good around dogs after a long getting use to period or on leash never safe with strange dogs but great with dogs she accepted never hurt them.