As Matt's love interest, María could have just as easily been a dolt – nothing but eye candy for Matt to swoon over. Luckily, Farmer gives us a fully-drawn character with a complicated family life instead. Farmer also got away from traditional hero tales by making María less than perfect. In fact, we don't mind saying it, María is downright annoying at times.
But let's back up for a moment and get the essentials. María is the daughter of a U.S. Senator, who seems to be in the pocket of El Patrón. In other words, María's dad gets various benefits from a shady alliance with Opium and is willing to let El Patrón continue to run his country corruptly. Plus, because they're cronies, El Patrón often invites the Mendozas to come stay at the Alacrán estate, which explains why María is there in the first place.
María thinks that her mom is dead, but it turns out she's alive and well – and writing books about the awfulness of Opium. So her dad is in with El Patrón and her mom is protesting against the same man. No wonder María is a complicated character.
Let's start off with her good, even admirable qualities. María is very passionate and loyal. She's willing to stand up to people and voice her beliefs. Plus, she tries to make good decisions in her life. She's one of Matt's greatest allies because she's able, eventually, to look past society's prejudices towards clones and give Matt his due as a human. María is also very brave, a quality she displays in scads when she tries to help Matt escape El Patrón.
If María sounds too perfect here, don't worry. She's far from it – like Matt. Both of them are quite human, which makes them a good team. María is overly emotional and prone to meltdowns. As a child, she's always crying. She's also extremely naive and immature. Her attitude toward Tom, while part self-preservation (El Patrón has arranged their future marriage), is also deliberately blind. She tells Matt, "I don't mind Tom - much. He's getting more like MacGregor, but I can change him." (21.50) Good luck with that one, María. We don't hold out much hope that Tom will ever be much more than a big fat bully.
María can also be extremely judgmental at times. We see this when she "forgives" Matt for killing Furball: "So I realized I was being unfair and should forgive you. After all, wolves don't know they aren't supposed to eat peasants." (16.22) How nice that she's forgiving Matt for something he never did in the first place. Plus, when you take a closer look at what she says, it's even worse. Basically, she's saying that Matt is somehow less than human – he's a wolf. So she can't really hold his nature against him. Of course he killed the dog. That's what wolves do.
It's an arrogant attitude to take, but it also reveals just how deeply entrenched social prejudices against clones are. Even María, with her big heart and generosity, can't quite overcome the values she's learned from everyone else. At this point in the novel, she can't bring herself to look at Matt as an individual, rather than a clone who just happens to be a nice guy.
That only happens later, when she helps Matt escape from El Patrón's house. When Matt declares his love for her, María responds, "I love you, too, […] I know that's a sin, and I'll probably go to hell for it." Good for you, María. She's breaking away from society and finally making her own decisions. In this romantic moment, María shows us that she's grown up a lot over the years.