Lucia Marquez (previously Perez) is Gabrielle's mother.
Lucia married Mr. Marquez, a factory worker. They lived in Las Colinas, Texas, and they had three children: Gabrielle, another daughter, and a son. Mr Marquez became ill with cancer and died when Gabrielle was five years old. Later, Lucia married Alejandro. Alejandro would get drunk on tequila and rape fifteen-year-old Gabrielle, who then was a virgin, and couldn't tell her mother about the abuse because she didn't think Lucia would believe her. At some point, Gabrielle ran away to New York and began a modeling career.
At some point, Alejandro was said to have died. However, in season 7, Gabrielle discovered that he faked his death.
She has dated other men, mostly rich, including the boyfriend whose break-up with leads her to show up at the Solises on Wisteria Lane.
Lucia shows up very much to Gabrielle's suprise, her reason being that she was left by her boyfriend and needed a place to stay. When Gabrielle finds out she may not be able to concieve children due to the injuries she sustained by falling down the stairs, it is Lucia who offers to be their surrogate. Carlos accepts the idea while Gabrielle seems reluctant.
The next day Gabrielle drops Lucia off at a hotel telling her to leave her alone and then drives off abandoning her. Carlos tries to reconcile the estranged mother and daughter but when he talks to Lucia about Gabrielle having been molested by her step-father Alejandro, Lucia brushes off the gravity of the thing, saying that she knew Gabrielle willingly seduced Alejandro to make her jealous, and she had forgiven her. Carlos then realizes Gabrielle was right about Lucia, and leaves her at the hotel. Lucia has not been seen or heard from since.
Lucia is very opportunistic, always trying to take advantage of people in need. For example, she suggests to become Gabrielle and Carlos' surrogate because this would assure her security, as they are very wealthy. After Carlos abandons her at the hotel, she is seen talking on the phone to an aunt who has had surgery and insisting to come stay with her and help her.
It is also very possible that she is a gold-digger, as she has dated many wealthy men for their fortune.
Her looks are also very important to her, as she has gotten a lot of plastic surgery. It is possible that she resents Gabrielle for her beauty and her youth, and that she tries to compete with her. She is also very exhibited and proud of herself, not hesitating to flash her daughter and step-son to show them her new breast enhancement surgery, and dresses very skimpily around Carlos, which makes Gabrielle uncomfortable.
Lucia and Gabrielle have a very tense relationship and both carry a lot of resentment towards each other. Lucia seems very jealous of Gabrielle because she has been more successful than her in life, having a great career, then marrying a wealthy businessman who loved her, and living the American Dream in a wealthy suburb . Gabrielle knows Lucia is an opportunist, and is against her becoming their surrogate, knowing they'll never be rid of her. She is also presumably angry at her because Lucia knows Carlos' very strong desire for a child is his weak point and uses this to manipulate him into convincing Gabrielle to be cordial and welcoming towards her mothe.
Gabrielle's resentment of her mother is traced to the fact that Lucia did nothing when Alejandro raped her fifteen-year-old daughter. As it turns out, Lucia knew about it, but is convinced Gabrielle willingly seduced her husband and had an affair with him.
Lucia knows Carlos wants a child more than anything, and is aware of the couple's difficulties to concieve or adopt. She suggests becoming their surrogate, knowing that Carlos will forever dote on her and give her a saint-like position in the family, not unlike his own mother. Carlos indeed falls for that, insisting that Gabrielle treats her mother with more kindness and forgives their past disputes.
Lucia, certainely because she is convinced that once her daughter made a move on her then-husband, doesn't hesitate to try to seduce Carlos when he comes to see her at the hotel, wearing suggestive clothes, and asking him to zip up her dress.
When Carlos sees Lucia doesn't believe him when he tells her her child has been molested by her ex-husband, he realizes that she is a cruel heartless woman, and takes his wife's side, abandonning his step-mother and potential surrogate at the hotel.
Given that Lucia wouldn't believe in the abuse of her child which took place under her own roof, it shows that she was devoted to her then-husband Alejandro, or at least afraid to be alone. However, she was convinced he cheated on her after being seduced by his step-daughter. It is unknown if Lucia and Alejandro split up before his pretended death or if he disappeared and spread a rumour of his death while they were still together, thus making her a widow.