I just think she was a little inconsiderate?

My 13yr old son spent the night at his friend's house, and he called me at work 9pm upset saying Billy was treating him bad and he left at the park.So I called my boyfriend he doesn't drive but he said he would ask his mom, she said she didn't have any gas. Now before she got her car I have let her take my car to run errands,and this is how she wants to treat me in my time of need, I know my son is not her responsibility.But I thought that was rather inconsiderate. One a child needed help and I have actually let her use my car when she didn't have one..