Initially, Rosa comes across as quite a sympathetic character. After Matt cuts himself badly on the broken glass of a windowpane, Rosa shows herself to be a very caring person when she comes to his aid, picking shards of glass from his hands and feet.
But Rosa's tune suddenly changes when she realizes that Matt is a clone. Matt's status is revealed by the writing on his foot that identifies him as “Property of the Alacran Estate.” Once she knows Matt to be a clone, Rosa immediately turns against him, and she picks him up and unceremoniously dumps him outside the house.
Before long, Rosa is subjecting Matt to a regime of unspeakable cruelty. As Matt has now been outed as a clone, Rose regards him as nothing more than an animal. She thinks this gives her the right to treat him with considerable cruelty, and that's precisely how she does treat him. She locks him away in appalling conditions and subjects him to constant abuse. Rosa's treatment of Matt is so bad that he doesn't just become traumatized, he even develops asthma. For good measure, Rosa even has the audacity to blame Matt for messing up her romance with Willum the doctor.