BluesDancer: Try this interactive webpage re: Beretta 92
http://www.genitron.com/Basics/Beretta92/New-Beretta-92.html
It's all very informative, but the button marked "The Trigger and Firing Pin Catch" will graphically depict the actions/relationship of trigger, trigger bar, and trigger bar spring.
For practical purposes, if your trigger bar spring snaps in half or falls off the side of the weapon, you will immediately notice a loose trigger that has no tension (trigger feels exactly as if you had applied the safety...except that the safety lever is on "Fire"). The weapon will not fire.
This is a good reason not to get too agressive with cleaning brushes or rags when cleaning under the right grip plate. The spring can become dislodged or partially displaced from its slot, then covered up by the replaced grip plate, and not discovered until it 1) breaks or 2) completely slips out of place. Always do a visual check before replacing the right grip plate and ensure that the spring is properly in place. Check that the grip plate screws are snug after you replace the grips.
Instructor Tips: Have her dry fire before you ever go hot on the range; this allows her to get used to the weapon's grip, trigger, and manipulation.
Have her start firing at the closest range possible (3-5 yards is ideal). This allows for instant visual feedback (she can see every fresh hole open up on the paper) and allows her to easily and quickly put "body english" corrections to her grip, sight picture, and trigger pull. When she is demonstrating good control and can place the rounds in a shot group, back off to 5-7 yards. If she (or anyone else) tells you that 3 yards is "too close"...tell her that US Special Forces routinely warm up at this range while shooting 1" dot target pasters and that most self defense shootings are at about that range (and inside of 7 yards). Don't allow a first time shooter to shoot at 10, 15, or (God forbid) 25 yards. Point blank is best.
Keep instruction simple. Cover a point and then briefly demonstrate
only that point (or simply allow her to try it). Once she gets shooting...let her shoot. Don't step into her space and offer corrections of every other shot she makes. Don't multi-task a new student and don't talk too much. Keep it light and fun. If you act that way, your student will feed off of you and enjoy the learning experience.
Good luck with your instruction.