Protective or Aggressive Behavior?

I have 2 standard Aussie males. Both fixed. Father and son. 13 and 7. No problems with them at all. I also have a 1.5 year old mini female. A couple months ago she started fighting with our 13 year old male. For no reason just attack him. Then the other steps in and have a 3 way dog fight.

I'm currently 35 weeks pregnant with our first child and as you can imagine this is a concern of ours. Outside of the random attacking of just the one dog, not the other one, she is perfect. Smart, sweet, gentle, minds, pays attention. Good with other people and kids and babies. Well socialized.

We have barely spent any time training her and she acts better than our older two. I've been watching her closely lately and when she goes after our older one it's usually because he's trying to come to me. There's never a toy or bone or food involved. Just me. Since becoming pregnant she has been more attached to me. And she's always trying to keep our older dog away from me and gets between us. But not the other one.

I'm nervous with the baby on the way that she will be too overprotective. Of me, of the baby. That she won't let either dog near me or the baby and we will have more fights on our hands.

Any suggestions of how to help, or know why she is acting this way?

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