Derived from Alligator. 'Gata' is slang for Gator
The alligator stays hidden in the water until some unsuspecting prey comes to the waterhole to drink, then it attacks. The waterhole is a place where most animals exist together peacefully, the cheetahs drink from the waterhole next to the antelope. It represents a social setting of sorts, where all the animals coincide. The Gator on the other hand, creeps steathly in the waterhole and preys on other animals when they aren't ready. The gator, or "Gata" victimizes other animals to get what it needs.

"Gata" is used to desribe a sneaky, scandalous person.
A "Gata" would go after a vulnerable person or someone who is easy to take advantage of and usually strikes quietly, without warning, when you least expect it.
Someone who shows no love for anyone else.
A 'Gata' is usually willing to fuck over his friends and family for his own benefit.