He may not have intentionally steered you wrong. He may know the proper husbandry practices of plenty of reptiles, but isn't too knowledgeable about retics.
However, like I mentioned earlier, and like bcr said, the shed cycle starts as soon as the old skin is gone. So for him to say just a soak is enough is way out there. That's not true of any species of snake that I'm aware of.
Don't beat yourself up. Use this as a learning experience. This is why I advocate so strongly for doing independent research and cross referencing info.
I honestly believe you and your mom would benefit greatly by researching together. Make it a fun, bonding experience if you can.
Quite simply, the more we know about our animals the better we can care for them. So sitting down with your mom and learning together could ease a lot of stress for both of you as well as your snake.