Is she still swallowing or fighting the syringe?
Guinea pig teeth have one of the fastest growth rates of all rodents because of the very abrasive silica in the grass fibre, which is the food source they have evolved on. Once the regular grinding down process in the molars at the back can no longer happen, the premolars will grow very quickly spurs that bridge over the tongue and trap it.
In the first case the overgrowth may be so great now that she cannot chew anymore. Please continue syringe feeding and offering water (NOT just water because a piggy doesn't need to chew to swallow syringe feed but you can soften it a little more to make it easier to swallow). Don't give more than 0.1-0.3 ml at any time and wait until that has gone down safely before giving more.
Not Eating, Weight Loss And The Importance Of Syringe Feeding Fibre
In the second case, if she is actively fighting the syringe, she will be unable to swallow or to process food.
Emergency, Crisis and Bridging Care until a Vet Appointment
Please see a vet as an emergency as soon as you can.