Some deacons do, some don't, it depends on the local bishop.
My grandfather became a priest without going to seminary, my father was a deacon for 28 years after graduating seminary, before becoming a priest. I know many deacons who didn't go, but then, many who did. All up to the bishop.
How did yr grandfather do that.
I know in the canons schooling not a requirement but nowadays you need a masters in div to be a priest.
In the good old days your Biship would do the herotonia over your head and u were a Priest.
How long ago did your GF become a priest.