but the new owners said that the cat should only eat mice.
What? That new owner clearly have no idea how to raise a cat. Poor cat forced to live with mice alone -_- Thankfully, you adopted them because clearly she wouldn't have survived if there was no decent house that would shelter her cat family. That also happened to us before when Chicha, the mother of our four cats, was still the neighborhood cat. She was also once a stray cat, but we took her in because she kept bringing her child inside our house, and the funny thing is, she didn't stay inside our house with her kittens that time. She just put them inside, then went out to look for food, and then when she's fed, she gets inside and nurses her kids. That went on for months, as if she was shy to stay inside our house. When they were bigger, she even tried to carry them out, but we decided to adopt them all, and now they're part of our cat family!
Hopefully, those stray cats, especially those who are mother cats, would find a home that would welcome them because yes,
Motherhood is something that causes respect, admiration and sympathy!
and hopefully, more people get to understand that.