Statistical probabilities tell you EVERYTHING ABOUT EVERYONE and yet NOTHING ABOUT ANYONE.
Yes, if you take 1,000 people like your daughter then of those who live to age 65 or whatever, just about 550 of them are going to get Alzheimer's.
But each individual will have an ACTUAL rate of the disease of exactly 0% or 100%, and that 55% chance actually gives you NO information about which you will be.
And without those gene variations, she still might have a 10% say chance of getting the disease.
Behind the screen the DM rolls the dice. You don't get to see the results of the roll. Anyone who has played a D&D like game, or something like World of Warcraft which is so dependent on dice (random number generators) for the outcome of events, will know that it's hopeless to think too much about what the next roll of the dice will bring, because when you're rolling a lot of numbers between 1 and 100 on a regular basis, you're going to get numbers like 1,2,3 and, 98, 99, and 100 all the time, and you absolutely cannot develop any sort of intuition based on probability.
So lots of people with 55% chances will not get the disease, and lots of people with 10% chances will.
Even when your risk factor is 95%, there's no guarantee, and you should not be "surprised" if you turn out to have it happen to you after you thought you could just round the probability to the nearest value of 0 or 100.
People hate uncertainty. Given a probability most people will NEED to decide at that point whether the event will happen or not, because they can't stand to go through life in suspense. They will ask you "Ok, so that means I will get the disease?" when it means nothing of the sort.
A 55% chance to get terrible disease by age 65 is just NOT a reason to change your lifestyle IMHO.
For a good dose of reality, take 100 people age 65 and have them get their 23 and Me tests done and watch while they laugh at all the things they were at higher risk for that they DIDN'T get and all the things they were at low risk for that they DID get. If you do this (even for one sample, give a 23 and Me gift certificate to an older relative and see how much their results make you worry less) chances are it will make you worry about probability a lot less.
Statistics are great for determining insurance rates and public health policy, but they DO NOT ACTUALLY GIVE YOU ANY INFORMATION about whether YOU as a single individual will come out one way or the other.
There are a few "completely penetrant" genetic diseases (hemophilia, etc.) where if you have the gene then you WILL GET the disease. But almost everything 23 and Me tells you is about probabilities which are much less than certain and honestly nothing to get too worked up about.