Hello! Thank you so much for asking your question. I think your best course of action next time you see your neighbor is to roll down the window and ask her what she would like you to do, but I noticed a couple of misconceptions in your narrative that may give you a very different reaction if they aren't corrected.
Here is some info that might help you make a friend out of this situation.
1. I can promise you the guide dog is not reading what you are doing as a car and making choices unless you are about to hit your neighbor. Your neighbor went through a lot of training to learn how to get around town without her dog, then even through even more training with her dog so that she and her dog could work as a team. She gives the directions. Her dog walks in a straight line until told to turn, and avoids obstacles. He doesn't watch when is the correct time to cross the street or wait for people to wave him on. Your neighbor makes all those decisions. The only part the dog is in charge of when crossing the street is waiting for the forward command and disobeying if there is a car in the way. What you see as the dog trying to make a decision is probably the dog doing exactly what it has been trained to do, which is stop for the car and wait for the next direction from his handler.
2. Sometimes people with visual impairments travel more slowly or take time to listen. Your neighbor might look like she is waiting to cross the road, but really she might just be waiting or listening with no intention of crossing. Keep in mind if she is clearly trying to cross the street, that she might not be able to see you wave her on. She knows how to keep herself safe. Your car idling could be telling her it's not safe to cross.
3. Your neighbor no doubt has opinions regarding how she would like to be treated. The internet can give you their opinion. Mine is not to stop for her unless she is in the cross walk and actually crossing, but what your neighbor wants is what she should get.

I’m a guide dog owner. I was taught to wave in a car that does this. You may have stopped or slowed but the car behind you may not. The dog is trained to cross when there’s no traffic and to stop if there is a car present in the road nearby. So the best thing to do is to be mindful of course but to go so the dog can see if the road is clear behind you

I’m a mobility instructor. I teach cane travel skills to people who are blind or visually impaired.

The main way that I teach street crossings is on the absence of threatening traffic. This assumes that cars will maintain speed around the speed limit. By slowing down or stopping, you inadvertently lengthen the amount of time your neighbor has to wait to cross.

If this is at an intersection with stop sign or stop light control, then I teach the person to go when parallel traffic starts to go. This lessens the risk of being hit when you begin to cross the street.

So, if your neighbor is standing there waiting, she is likely listening for the flow of traffic and trying to determine when it is ok to go.