>> would she experience sudden loss of consciousness like that?
No, not at all. Nothing like that. It makes a person complacent, not unconscious.
http://en.wikipedia.org/wiki/Flunitrazepam
Here is a list of drugs, some of which can cause loss of consciousness: http://onestudent.org/wp-content/uploads/2010/09/common-drugs.pdf
The loss of memory happening so fast doesn’t make sense.