There's really no secret made about the fact that Flemeth won't really die, and Flemeth doesn't even seem to particularly mind the prospect. And I have no knowledge that whatever they're working on will actually be harmful to me; IC, I believe I would have seen Morrigan's facade crack more if she thought I'd come to harm.
I'd say Morrigan has you wrapped around her finger and using you as a tool, you being convinced she's madly in love with you. Let's re-cap:
- she deliberately keeps things from you, and even if directly asked, refuses to give you details on her plans or the ritual
- no matter how much she "loves" you she still leaves you and asks you not to interfere
- she is shown to be a person of poor morals, gladly sacrificing others for her own goals. Supportive of blood magic and murder of many innocent elves. Supportive of you leaving Redcliffe and it's people to die. Truly a woman of impeccable morality and a great rolemodel for any child - even moreso for a child with godly powers
- by her own admission she considers men gullible and easy to trick if you convince them that a women is madly in love with them.
"Men are always willing to believe two things about a woman: one, that she is weak, and two, that she finds him attractive."
(Delivering Notice of Death) "Your man is dead. Get over it." or "Oh please. I am so sure I am the one who has to do this."
Morrigan: There is nothing to notice. What you call "love" is nothing more than a wishful fancy.
Morrigan: Let me tell you one thing, and then let us speak of it no more. Love is a weakness. love is a cancer that grows inside and makes one do foolish things. Love is death. The love you dream of is something that would be more important to one than anything, even life. I know no such love.
Shale: The swamp witch has the same arrogance, the same air of cruelty. I would hate for it to have possession of my control rod... if it still worked, of course.
Wynne: You are dangerous, Morrigan. Dangerous, cunning and thoroughly deceitful. But you are beautiful, and he is young. It's a pity he doesn't know any better.
Trusting Morrigan with the OGB is an act of stupidity.