Dallas has put up signs around the city saying "Say No to Street Charity," as in, don't give cash to panhandlers. I'm reasonably sure this campaign isn't managed by cold-hearted bigots who simply think everyone out there is a worthless drug addict that doesn't need help. Some sort of study has been conducted indicating cash from strangers contributes to problems more than it helps and there are better solutions that the city itself, along with whatever charitable organizations are addressing this, are doing their best to provide.
I was like this woman when I was a teenager as well. I not only did what she did, but I went well beyond that. When I got my first car, I drove into LA's skid row at night and handed out whatever cash I had to whoever I could find, at least once a week.
Much later in life, nearer to now, I actually lived in a major city downtown district. Frankly, the experience left me feeling hopeless in the face of a problem the scale of which no single person could ever hope to have a meaningful impact on. I started walking for several hours a day as part of my spinal rehab 8 years ago and I'd be stopped every 50 feet at times by people asking for money. This wasn't even just homeless beggars. It was often fundraisers for political campaigns and charities. This left me not only with the impression that I could spend the entire day handing out cash and all that would happen is, as much money as I make, I'd end up broke giving out thousands a day, and still not make any dent, but more practically speaking, I'd get no actual walking done. Being stopped three times a block by all the people demanding just a minute of my time adds up to a lot of minutes, leaving nothing for anything else.
It's a similar problem to retention marketing. Every single business you have ever done business with or even looked into doing business with puts you on a permanent list to send you updates of every promotion they ever run. To them, it's perfectly rational. Some evidence suggests the rate at which this turns leads into sales exceeds the cost of sending the messages. Collectively, however, if you even bothered to read all the e-mail and SMS and answer the phone calls, you'd have no time left to do anything else. You wouldn't even be able to eat or sleep.
To me, the only rational response left is to turn off and ignore all of this. I don't have the capacity to do individual triage. If I tried to evaluate which beggars need money the most or which spammers trying to buy my house might make a worthy offer, that would take even more time than simply listening to or reading all the spam. Even if I wanted to do it, it's not logistically possible.
This is probably not "optimal" altruism or anything, but fair or not, I've just retreated back into the circle of family and friends I already know. Plenty of them are hurting for money at times and I have never once hesitated to give it to them. I'm well aware there is no moral universe in which they are more deserving of charity than some distant kid in an impoverished, war-torn nation, but there are tens of millions of such kids and I can't get to know them the way I know my own family. I already pay taxes, and as far as I'm aware, though governments do a far from perfect job of this, their basic purpose is to address these kinds of large-scale coordination and knowledge problems that individuals can't possibly hope to address on their own.