Totally normal! And bp's are smarter than a lot of people give them credit for (as 100% dumb and thoughtless animals), and they do learn certain things through conditioning. If you haven't handled a mouse or rat, they're smart enough to know your hand isn't food, even if they might be expecting food when you first open the cage. Assuming they're not in feeding mode.
For all my snakes, I reach behind them first and lift their hide off their back. I also try to approach from the side and behind them, stroking their back first, and not reaching toward their face or from directly above. If they don't turn around toward my hand in that quick food way and zero in on my hand, it's safe to know they won't strike at me.
To know if she wants to strike at you, you really just have to reach in and go for it LOL