yeah it's best not to do it. You can injure the snake. It's a guess, you got at least a 50/50 shot, and judging by the photo I'm say a little girl, but that's a guess too.
It's super easy to tell with Boas. The male boas have hooks next to their vents, (the remains of hind legs millions of years ago.) But when God created Corn snakes I guess he wanted to watch us scratch our heads.