Ariel Winter's Mom -- I NEVER Called My Daughter Fat

Ariel Winter's mother told the court ... she NEVER trashed her daughter or called her fat ... despite allegations to the contrary ... TMZ has learned.

Chrystal Workman filed a declaration with the court, obtained by TMZ, in which she fires back at allegations made by Ariel's older sister Shanelle ... that Chrystal would constantly say horrible things to Ariel.

In the docs, Chrystal says, "The allegations in [Shanelle's] petition are untrue. I have never put Ariel down or told her that she is overweight."

In fact, Chrystal says she constantly told her daughter that she is "smart, beautiful and talented."

"Since birth, I have loved and cared for Ariel in all her physiological and emotional needs," Chrystal says ... adding, "I have always been her caretaker and looked out for her best interests."

We broke the story ... Shanelle was awarded temporary guardianship of Ariel over allegations that Chrystal physically and emotionally abused Ariel. Chrystal has denied the allegations.

In the docs, Chrystal also claims Shanelle is only using Ariel as a "stepping stone to further her own career as an actress."

Chrystal says Ariel makes $75k per week from "Modern Family" alone ... and is concerned Shanelle will misuse the money to buy herself a new house.