Am I in the wrong for refusing to continue offering free childcare for my stepdaughter?

I decided right then and there: I was done.
A few days later, Alice called again. “Mom, the daycare dropped Ellie. Can you start watching her again?”

I took a deep breath, steadying myself against the kitchen counter. “I’m sorry for your situation, Alice, but I can’t do it. I don’t feel comfortable watching Ellie anymore.”
“Please, Mom,” she sobbed. “We don’t have anyone else. I might have to quit my job!”

“Maybe you should have thought about that before letting Sam publicly humiliate me. Before liking his cruel post.”
“That was stupid, I know,” she admitted. “I just… I felt trapped between you and him. Please, Mom. We’ll do anything.”
“I’m sorry, sweetheart,” I whispered, tears rolling down my cheeks. “But sometimes ‘anything’ comes too late.”

Later, I found out the truth. The daycare hadn’t dropped Ellie — her parents had left because they couldn’t afford it. Alice and Sam hadn’t realized daycare didn’t provide essentials like diapers, wipes, and formula. They’d assumed $350 a week covered everything. Sam had also been shocked to learn that one worker cared for five infants at a time.

Now, they were scrambling. Sam had to sell his dirt bike, and Alice sold all her designer handbags to afford their child’s daycare.
My husband and stepson think I should reconsider for Ellie’s sake. “Sam’s the problem,” they argue. “Why punish Alice and Ellie for his behavior?”