I don't see what people are confused by. It pays $1 million a year for life, with a guaranteed minimum of $20 million. If she gets hit by a bus tomorrow her heirs will collect another 19 payments. If she lives for 100 years she'll collect another 99 payments.
" there are plenty of contests that offer lifetime whatever and they are not infinite. They have a finite number of whatever may it be ding dongs or razor blades and once you use them up it is over."
In your case you're confused about the difference between a lifetime and a "lifetime supply". If you use more razor blades or eat more ding dongs than normal people you'll use that supply faster than normal people. Just because they promise you a "lifetime supply" of ding dongs doesn't mean they're going to give you enough to make ding dongs 95% of your diet. Just like the lottery, they cover those details in the full rules, for anyone who wants to read them.