Hey Zara,
Kids are so innocent, its just sweet.
My DD sounds much the same, she is too friendly. Will talk to absolutely anyone, and sometimes it breaks my heart if its to another kid, and that kid tells her to "go away" or something rude. I feel like it crushes her little spirit..

Maybe you could tell her that only her dog is for patting/playing with? (In a way she could understand, obviously). That way she will know not to go near other dogs (whether they be vicious or not).

I have no idea about the stranger danger, I guess she is still a bit young to understand the whole concept.

x