1. She is "crouched" over "tightened up" like you do with stomach cramps when you are "holding on."
2. She asks if it will take long.
3. The others in the tub don't make any moves like they know what is coming next.
4. If you watch it a few times when she stands up you can see the "accident" ....well, you know what I mean.
If it is fake, it is a good fake.