Ranai made some excellent points. I jumped in without asking you more questions. Please forgive me if my other post was too harsh.
Rant alert: Grrrr!
Dangerous play - with yourself or others is one of my pet peeves and I tend to go off the deep end when I hear that someone has been harmed by their over enthusiasm. Couple that with a friend lost to suicide, and another friend who works in the court system - who is constantly telling true tales of people who had died while having too much unsafe fun leaving family members to pick up the pieces and well, what can I say, its a pet peeve.
:blabla: :soapbox:

nt:
Back to your question...more information would certainly help others give you better advice. I'm sure that other masters or submissive must have dealt with a similar problem. So:
How long have you been with this slave?
Is she really your slave in the contract sense - 24/7, did you just happen to use that word, or is she your playmate sub or sometimes bottom?
Has this type of thing happened before?
Where was this 9 inch monster - mouth, vagina, anus?
(You said she fainted, so I assumed mouth.)
Is she your first slave?
One of many?
Whatever else you a willing to share?
Best wishes through this difficult situation, Ruby