Just a wild guess, I wonder if that incident when Laci was attacked has made her frightened of other (large) dogs, as she sounds as if she's ok with smaller dogs. Yes, one incident can cause a lifetime of issues. Barking at the fenceline is normally more a fear reaction that a dominance one. I have a dog that fence fights and barks at other dogs - he was attacked as a pup.
My other thought is that Laci is resource guarding either you and/or the couch from that huge intruder. In her mind, it and you are hers and she WILL NOT share with that icky (her words, not mine lol) puppy. Since she will play with him and tolerate him in other areas, I am leaning toward resource guarding.
You may want to work on both issues. It'll help in the long run since every time she practices bad behavior it becomes easier to repeat it.
for resource guarding:
Resource Guarding: Treatment and Prevention
here's a starting point for the reactivity toward other dogs:
Barking & growling, signs that trouble is brewing | Trisha McConnell | McConnell Publishing Inc.
Best wishes