Popping adults takes quite a bit of gentle strength. The easiest snakes to pop are hatchlings.. it gets tougher from there, once they gain more muscle control.
I def. think that this person needs to get the snakes to an experienced person to probe them for her. Popping and probing can be harmful to the snake if they are done by someone who doesn't know what they're doing; it is something that needs to really be watched, to learn..
I know that I personally suck at it! Luckily my husband has a hidden snake-sexing talent.. works with me.