It sounds to me like she has been a house cat. She must have been around a fenced yard to and this all seems familiar to her. If it's because someone threw her out or if it is because she is lost is anybodies guess. She sounds like a real sweety and since she is so friendly it doesn't sound like she was abused. But we all have different ideas of abuse too! Some of the friendliest cats I have ever seen are the ones that get totally ignored by people and they are starved for affection.
I would ask your nearest neighbors and people in the area you trust to be honest if they have ever seen her of if they know someone who is missing their cat. You could post a few flyers but I wouldn't put a description at all! Let them tell you so you know it isn't someone who will sell her to some lab. If you can run an add in the local paper just saying found cat in such and such area call with description. Oh and another thing I would do is call your local shelter and see if anyone has called them looking for her. I know when Leroy was missing that is one of the first places I called before checking with all the local vets.
My guess is that she is yours! You never know though and someone could be frantically looking for her. It would be nice to think that is the situation but as we all know that probably is not the case.