Gut, that lady sounds like a freak! I can't believe you have to deal with people like that...sheesh!
snark, you did a good deed and the recipient of that good deed (your neighbor) thanked you, so that probably made you feel good. I wouldn't try to second guess why the police were so suspicious of your activities. I think in a lot of cases, they want to protect the female--and maybe they were overzealous in your intentions. Maybe they were just racists getting off on their power. You did a good thing and I thank you for taking the time to help someone who needed it.
When I do something to help someone, I do it because I want to and, on a selfish level, I know that it will make me feel good to do something nice. Sometimes it does backfire, but more often than not it's good all around. The really annoying time is when I stick up for someone and that person doesn't reciprocate. Usually that's in a work situation, where some weasely manager will be going off on someone, I'll stand up for him or her, and then the tirade gets turned against me. But no one has the balls to stand up for me including the aforementioned colleague who will just silently sit there and watch me get attacked. I find that annoying, but not unexpected. And I just defend myself then. I guess my feeling is I can take care of myself, but some people need our help.