Although I don’t believe this cover story one bit, people do react differently when on drugs. If they are in a different state of mind, there is no guarantee how they might react because of the dreams they were in at the time.
The Ambien excuse seems pretty lame in this context, as it would get demolished by those expert in its side effects, which tend to be sleepwalking doing something that would otherwise be boringly normal for waking.
Are you insinuating that she was on drugs?