Other mistake: During the bar gunfight, Banderas shoots the ventilator that falls down on the bad guy. In the next shot, you see that the ventilator is still rotating. The ventilator should be disconnected after falling to the floor, since the wire isn't that long.
Factual error: During the scene where Navajas is throwing knives at El Mariachi and then the Bucho gang in the limo, he slides down in front of the car. The license plate simply says "Mexico" under the serial. Actual Mexican plates of the time period in the movie use the official state abbreviation followed by MEX to identify the state of issue. For example, JAL MEX for Jalisco, which is where the JWF685 serial seen on the plate would have been issued.
Continuity mistake: When the knife throwing assassin is after El Mariachi, he throws the first knife at his left arm and the second one at his right hand. Then we see El Mariachi going around the corner, with most of his back out of view, as the assassin throws the third knife at him. A few moments later, we see El Mariachi taking the knife out of his back - it's right next to his shoulder, and it was impossible for the assassin to hit it from where he was.
Continuity mistake: Near the end of the film, Antonio Banderas calls his friends and holds the phone in his left hand. The camera cuts to Salma Hayek and then cuts back to Antonio where he is seen to have the phone in his right hand.
Continuity mistake: When the fight breaks out in the bar during the opening song with El Mariachi and his bandmates, he motions for them to join him to break up the fight. After he breaks it up his bandmates reappear on stage like they never left.
Continuity mistake: After Antonio Banderas saves the boy from the truck, they are walking beside a building. The guitar the boy is carrying flips over with every shot change. First, the strings are facing the boy's leg then the guitar back is facing the boy's leg. It changes 4 or 5 times.
Other mistake: In the bar fight/shoot out Antonio Banderas shoots a fan onto one of the gunmen and we see the man fall down face first into the camera with the fan on the back of his head, Antonio walks around the bar and guy is suddenly laying on his back and turned completely around with fan on his chest.
Audio problem: When the kid shows El Mariachi how he plays, you can hear the part that he's not playing because it's a constant sound on one string and he's stroking all the strings at the same time.
Continuity mistake: When the little boy is giving his fathers guitar to the drug runner it has no strings, but when the drug runner gives it to Antonio Banderas it has a string.
Revealing mistake: When Antonio Banderas runs over the guy at the end of the big shoot near the end of the movie, the guy getting run over has been replaced with a dummy. You can tell because of how easily it moves and how much it twists. You can also slow the film down to see that the dummy's plastic hand is visible.
Continuity mistake: Antonio Banderas throws his guitar case across the roof, then jumps after it and opens it. From the reverse angle the fake guitar inside is still in place, we then switch to it from from the front and it's instantly raised, with the guns visible instead.
Audio problem: When the bad guys in the car are shooting at Danny Trejo, the kid with the broken leg kills him with six shots we see and hear, but the slide on his gun locks back after 5.
Continuity mistake: When the man sitting next to Tarantino is shot, in one shot there's no blood on Tarantino's face and neck, but in the next shot there is.
Visible crew/equipment: When Banderas and Catalina are on the rooftop, and Bucho shows up and Banderas doesn't shoot. When they start going to the next rooftop, you can see a shadow of a microphone going up the wall.
Revealing mistake: In the fight scene in the Tarasco bar, one of the bad guys jumps on El Mariachi, but he stops him with his feet and pushes him off and shoots him as he is flying through the air. As the bad guy is shot, you can see the tape holding the squibs on his shirt.
Continuity mistake: After the boy gets his right leg broken by Christos in the fight scene at Bucho's villa: [1] The boy begins to stand up (straight, without turning his body). In the next (bad) cut his movement should be continued, but he suddenly is erecting in a 360°-turn finalized by jumping in the air to knock Christos down with his foot. [2] If you would look down at him from above the scene, his right leg would describe a clockwise movement towards Christo's face. Look sharp and you will see that it never reaches its aim because the distance between the two men is too long. Before the foot hits its aim another very bad cut is set. In this one his leg would describe a counterclockwise movement, not clockwise as the movement has begun the cut before. To accomplish the motion instructed by this cut, the boy would have had to stop his leg's movement abruptly in the middle of the foot-kick, when the foot has the highest speed and force. There he would have had to fling his foot back where it came from to finally knock Christos down. And all this without having any footing from the ground whilst his jump.
Continuity mistake: At the very end when his girlfriend picks him up, Banderas throws his guitar ahead of him. But in the next shot it's underneath the car. He had to twirl around to throw it, but it only went as far as the car he's standing next to?
Revealing mistake: When Antonio Banderas shoots the guy with the broken ankle at the beginning of the shoot-out on the roof near the end of the movie, he falls off. Slow-mo his fall and you'll see the air mat he's suppose to land on, it's a huge evenly raised lump in the sand about a foot high and surrounded by white rocks. He even sinks into it when he lands.
Continuity mistake: In the fighting scene with Antonio Banderas and his two guitar friends, before everybody starts shooting we see the little boy walking around strumming his guitar. In that first shot the strap is crossing the back of his neck. But in the very next shot of the boy, that rope is hanging down almost on his knees.
Continuity mistake: When Selma is stitching up Antonio after the knife throwing scene, she is seen on the bed putting on a band-aid, then reading a magazine, then tightening the bottle of medicine that she put on his arm. All while Antonio never moves.
Answer: Having a tough-looking, silent henchman/henchwoman is a pretty common trope in action movies. She's basically there to look tough and mysterious. I wouldn't read into it more than that, especially given how minor the character is. (Minor enough that I had to Google her, because I couldn't even remember her, and I've easily seen this movie a dozen times over the years).
TedStixon