She shouldn't have taken such a large position in a single stock. As a retail investor, that is stupidity.
As a retail investor, it is your job to find someone who knows what they are doing and can teach you how to invest or manage your investments for you. After that, if you are investing over 10% of your portfolio in one stock you are asking to be broke.
Your car analogy doesn't work because there is really no way to diversify your car whereas there are plenty of ways to avoid this kind of bad decision with your investments.
As a retail investor, it is your job to find someone who knows what they are doing and can teach you how to invest or manage your investments for you. After that, if you are investing over 10% of your portfolio in one stock you are asking to be broke.
Your car analogy doesn't work because there is really no way to diversify your car whereas there are plenty of ways to avoid this kind of bad decision with your investments.