Once Rei Furuya left to execute a mission, the originally "delicate and frail" Grenache instantly returned to normal.
Although the drugs injected by Sherry were real, and the electric shock interrogation was also real, Rum was certainly not willing to let such a useful tool be scrapped. Therefore, after the interrogation ended, he had her injected with a newly researched potion from The Organization that accelerated recovery. Combined with Mao Akai's special physique, that was why she recovered so quickly.
Her previous fragility was entirely put on because Mao Akai discovered that Rei Furuya easily fell for that routine, so she purposely faked it.
Chapter 56