Nah, your large intestine alone is around 5 feet long (coiled around your belly), and this is shorter than that; it probably hasn't even reached her small intestine which is another 9 feet are least. These "colon snakes", as they are often called, have to be bendy and floppy to follow the curves inside. If it were a big rigid thing of this size, you're absolutely right - it would make a terrible mess inside her, and it would be game over.
i think it could go up that far, hotkinkyjo can get some really wide ones inside her, its pretty flexible. usually you can see the belly bulge though, so maybe something fake