Phone card

I am at the airport and talking from one of the public phones instead of using my American cell. I notice a woman behind me, waiting for the phone. Indeed as soon as I am done, she comes forward but she does not want the phone, she wants to talk to me. She is asking for my phone card. "I'll pay" she says, "I just need to give a phone call". I shrug her off rather rudely. "I need that phone card too, you know, why don't you buy one for yourself?"
She looks at me and stutters the words "no money". I don't even think about how she was offering to pay for the phone call a second earlier but smile a nasty smile that says "find another sucker!" and turn around to sit down as I have to give another phone call in 10 minutes.
As I am turning to sit, I catch a glimpse of the woman and something in her eyes catches me off-guard. Maybe she really needs help. I feel overwhelmed by guilt and turn around with my open wallet. "Here is 5 Euros," I tell her, "you can go to the closest post-office to buy yourself a card." There is a post office in the airport and the sign for it is right above us. She takes the money and disappears in a minute. My guilt is gone. I think I've just been scammed of 5 euros.

Then she is back, with a card that she flashes in front of me. I have to give a phone call so I end up dialing as she is standing. I asked her "What is happening to you?" and she starts crying, saying that no one came to pick her up. I take my most gentle tone to tell her, as if to a child. "But they'll come, don't worry. You are not going to stay here for the rest of the day."
Her sister has apparently mixed up the dates. She is traveling with no money, no credit cards and her cell phone is not working. I try to reason her. "Don't worry. You'll eventually talk to your sister!" I remember it happened to me once. I waited for more than an hour at the airport as it was closing down finally deciding to take a cab to my friend's house. He thought I was arriving the next day. I was lucky he was even home. I remember the wave of relief that overcame me when he opened the door, all the tension disappearing at once.

She is calmer now, waiting to use the phone.
I go back to my seat watching her talking on the phone from a distance. Then she is in front of me, handing me back the card. "Thank you so much! I didn't use it all." I want to say it was no problem, but my body language is dismissive again and I make a gesture that could be interpreted as "whatever, I don't care". In a minute she is gone, leaving me with the card in my hand.

I hesitated about checking that card at the nearby phone.
When I do check it and find that the card is indeed almost full, I feel guilty again.
Doing good has never felt so wrong.