I'm sorry I don't know about the vets/rescues in that area, but I did find an internet seach and the only thing that came up for Tyler, TX is a Humane Society which I posted below. Perhaps you could call them to inquire what to do with mama and her kittens?

Tyler
Humane Society of Smith County
1823 County Road 386, Tyler, TX 903-597-2471

Healing vibes for mama and babies.