I was tryna help a homeless woman

I was walking out my apartment today and i saw a homeless woman digging through the trash. I felt bad for her cause she had a baby with her and i thought she must be like 25 or something. I went back up to my apartment and saved food and 3 bottles of juice. When i gave it to her, she said she was only 17. i felt disgusted and left. she said "have a great day" and everything. usually when i help the homeless they are atleast greatful. i dont really know what to feel anymore. I thought i was doing a good deed and i felt better but after she said she was 17 i felt disgusted. why and how is a 17 yr old woman on the streets? i cant wait to move back home. im done with this place.