Why is my Alternator overcharging

If the alternator is indeed overcharging then, yes, it may have fried the battery. Most likely, the alternator's internal regulator as failed, causing the overcharge condition. The regulator is controlled by the powertrain control module (PCM). As always, I recommend taking your vehicle to a professional repair facility to ensure it's diagnosed and fixed properly. Here is a list of reputable shops: https://repairpal.com/repair-shops