It is dreadful that people do these things. However, I am not too shocked either... Heck they dump their own children too, so nothing surprises me anymore.
I am glad that you can look after her for a while, and hopefully your neighbor can give her a new, loving home. She sure looks sweet. She is a small dog too, my gosh just how much trouble could she have been? Whoever, dumped her in your yard knew that you are a animal person and I believe picked you because they knew the dog would be in good hands.