I don't thin this is a nip in the bud type behaviour I am afraid.
I expect there have been signs before but they have been less obvious and hence she has now had to up her game to get the desired effect.
This will not go away on its own and if not managed correctly can get a lot worse.
If the behaviour has just started I would pop her down to the vets to make sure there is not underlying health issue or pain that may mae her react like this.
I would also check the food she is having - what are you giving her however if that has not changed that will not be the cause but may help her feel better if on a good food.
I would use a counter conditioning/desensitising approach.
You say with smaller dogs she herds them and drags them around so this too is inappropriate behaviour and she only needs to meet a feisty dog that does not tolerate that behaviour and you will have a massive dog fight on your hands.
The first thing to do is to not let her approach ANY dog off lead.
Have you got a good recall?
Can you walk her in quieter locations?
Have her on lead for this. Can you watch her really carefully at what point does she start to react to the dogs? By react she may turn her head, she may yawn, she may stand very very still, she may look away, she may raise her tail, lie down on the floor or just stare at the other dog.
This point is too close so increase the distance between you and the other dog (this is hard to do with just any old dog walker so you may need to get a friend with a dog to help you).
Then when she is more relaxed click and treat, do this over and over again but you must do it before any minor reaction - if she is lunging and barking then that is way to close. I would also be saying look dog and encourage her to look at the dog, (if you were told don't look or someone stand in front of you you would panic and expect the worst but if you could see the dog you would be calmer and feel in control)
You need to get to a stage that she can "look dog" without reacting or her training is too now see a dog and turn to you for a treat - you then have her near you to control the walking past dogs.
From now on I would never let her meet other dogs unless she knows them well and is relaxed. Dogs do not need to socialise with other dogs when they are adults most dogs should prefer the company of their owners so she is not going to miss out.
If she is on lead and does not react at all and you can walk past all dogs easily then that is your answer call her to you, reward her and walk past all dogs on lead.
This is a very tricky problem and most people need help with it as it needs to be carefully managed. Contact APDT and see if there is a trainer near you.
Do not listen to anyone who says you have to be cross with your dog, or use a rattle bottle, or says you have to dominant your dog - you will then have a dog that reacts to dogs and humans!
I guess you have a lot on your hands right now with babies and reactive dogs but it will need some time - I hope you can get some on the ground help.
You have got a mix of dog from two very busy and intelligent breeds. She will require exercise but she will need a lot of brain work and this will need to achieved and is more important than traditional exercise.
So clicker training would be great. Get her to learn the names of household objects - she can help fetch things when the new baby comes, get her to tug and then she can help you empty the washing machine and tumble drier. The busier she is in the house and the more her mind is full of other things she will relax more.