I do not think she would be wearing a cast if she was not hurt. There is a great deal of fakery in the WWE, but things do go wrong and thier are acciedents. Performers have broken their back or suffered concussions due to a stunt going wrong. It is quite possible this is similar.
On WWE SummerSlam last night, Sasha Banks lost the WWE Women's Championship to Charlotte just weeks after winning the belt on RAW. And WWE has removed Sasha Banks from the listings for their upcoming RAW live events. There are reports that Sasha has had pain in the lower lumbar section of her back, and is set to have an evaluation at the beginning of September. Only this can explain why she was unable to defend the championship last night.
I cannot imagine someone would go through lengths of faking a concussion and losing her chance at the title. More and more is becoming known about brain trauma and the repercussions of traumatic brain injury, both short-term, and long-term. Side effects such as cognitive impairment and issues effecting movement and balance as well. She lost the WWE Women's Championship just weeks after winning the belt on RAW and has been taken off the listings of RAW events. Pretty big blow for just a publicity stunt. Her behaviors seem more in line with an actual injury, rather than a faked injury.
Now it certainly is possible that she's actually hurt, even fake wrestling has the risk of injury. However, what matters most to the WWE is ATTENTION. And now that Banks lost in a SHOCKING twist of events, the organization can capitalize and keep its name in the papers longer if it milks this story.