I doesn't sound like your mom did anything wrong and if the snake and her both got startled I would say the best thing to do is have them both reset. Meaning slow down and let the snake and your mom see everything is ok. Rushing is and taking the snake sounds like a helicopter parent rushing in when their kid has a little fall. You have to let them learn they are fine and get through it.
As for handling I usually just do little sessions at first. Just to let them see I mean them no harm and that I am not a predator. With that I will go longer and longer reading the snake as I do it. Each snake and each day can be different. I don't stick to set times, days, or whatever. The only times I do not handle at all, unless necessary, is on feed days and the two days after. For example I have a baby King right now and she has been really great with handling. I am handling her more than I normally would because she is responding well to it. I check on her a few times a day and if she is out I may pick her up a couple of those times. She ate a pink this morning so the rest of today and tomorrow she will be left alone. After that I will go back to doing what I was.