I shockingly had the thought last night that I hoped my grandmother doesn't live long enough to vote in the 2020 presidential election
Isn't that cruel? Why'd you hope your grandmother dies before 2020?
I don't like her as a person, and I would like the country to move forward without her
However you feel about the direction your country is taking, it is wrong to wish harm on others for any reason.  One person's vote is not enough to change an election, and even if it was, this country is meant to be run as a democracy.
That is correct, one person's vote is not enough to change the outcome of an election.
I'm sorry you and your grandma don't have a great relationship, but don't you think it's unfair to want her gone for such petty reasons? Everyone deserves a vote in the country, even you. How about trying to have small political debates with her, so you can understand each other a little better?