The dog came into your yard? Many dogs do not like a strange dog coming onto their turf. Was this other dog a female? Same sex aggression is common in Rottweilers....this is part of the breed....
Just because she attacked another dog, does not mean she will attack people or your children.
Now you know that she does not do well with your neighbors dog, you will have to be extra cautious...because she will always remember.
How well socialized has she been? Has she always done well with other dogs?
Has she been to obedience classes? how well trained is she?
Give us some answers to these questions and maybe we can give you some advice.
Gina