We can't see exactly what the shooter did or did not do after experiencing a stoppage, nor can we see closeup pictures of the parts afterwards, but it does hilite the need for familiarity and training before shooting. What she should have done on experiencing this malfunction was;
1. keep the weapon pointed downrange (she did this)
2. put the weapon on "safe"
3. open the action and lock it to the rear
4. remove mag or enbloc with all rounds
5. inspect chamber, bore, and action for obstructions or broken parts and remove/replace them before reloading and resuming shooting
In the case of the Garand an out of battery detonation or a slamfire can be caused by either faulty ammunition or by mechanical defects in the rifle. Apart from obvious mistakes, like using the wrong powder, too much powder or a split case, proper case preparation and priming are critical when reloading for the Garand. Cases should always be FL resized and trimmed to below max OAL. Primers must be seated slightly below flush with the case head to prevent their detonation as a result of impact by the bolt face or the floating firing pin during feeding and chambering. Mechanical causes in the rifle could include insufficient headspace, a worn receiver safety bridge, a worn tail on the firing pin, a broken firing pin which is stuck in the forward position or an excessively long firing pin.
For the fastidious reloader a good check on proper case sizing is to use the rifle itself as a gauge. To do this strip the rifle and bolt down to a point where the stripped bolt can be closed on resized cases by hand (no influence of op rod spring, ejector, extractor or firing pin) and then try all resized cases in the chamber before priming and reloading them. You want cases resized to a point where they will chamber and allow the bolt to close on each case with no perceptible resistance. A bit of a crush fit is OK in a bolt gun where you have the power of the bolt's camming action to close the bolt on a tight case. This is not the case in a Garand where the action relies on the power of the op rod spring alone to close the bolt. Cases can be overly large, both in terms of the base to shoulder dimension and/or the case diameter and either will prevent the bolt from closing freely on the chambered case. This is why necksizing is not recommended for a Garand/M14 type.
A couple of other precautions when loading/shooting a Garand. Always pull back the op rod with the hand in a palm down position which will avoid any tendency to pull the op rod handle up and possibly disengage it from the bolt lug. Also, check that the bolt is fully closed after loading the initial round from an enbloc. Sometimes the action can be a little sticky, even with a properly lubed rifle (this is mostly evident in a newly re-parkerized rifle or with new parts that haven't worn in a bit). A bolt that is not fully closed can be seated by bumping the op rod handle with the edge of your hand.