Nothing in the Texas law requires the mother to cover up.
https://statutes.capitol.texas.gov/Docs/HS/htm/HS.165.htm#165.002
I don't see anything in that statute that prevents locations from so requiring, either.
“Maam you have to cover up”
“I don’t have to cover up. Feminism! I am woman!”
“That Muslim man is offended”
“I’ll cover up”
I breast fed my son 47 years ago. Always had a blanket. Nothing wrong with being discreet.