I'm having a hard time

I am hoping that fellow cat/kitten rescue people have been through what
I've been through.
I have a female feral calico that has had many litters, I can't trap
her, she is to smart for traps. I've brought several of her kittens in
over the past 3 years and got homes for them. But each time I bring
kittens in, they're usually about 3 weeks old I feel so guilty for
taking her babies away, even though I know they will have a better life.
I see her out there looking for her babies.
I just brought a new one in today, she just had one this time, it's
about 4 weeks old now. I see her outside looking for her baby and feel
so bad..
I would just like your thoughts on that, I guess I just want you to help
me to feel better, God knows I want to get her fixed, but she is so
wild, I don't think she's the greatest mother, because it is fairly easy
to get her kittens.
Anyway, thanks for any thoughts on this, and if anyone is going through
this I would love to talk to you, I feel so alone on this.

Aimee