I just can't accept her - she was a very, very close friend in addition to being a relative. We watched each other's children and hung out together all of the time. I refuse to have somebody that poisonous in my life.
I don't think you have to accept her in order to take your power back. You also don't have to forget in order to forgive (there's a good post about forgiveness that phd posted in the Infidelity section of this forum).
You don't have to be "friends" with her, or trust her, or even like her. You may have to detach from her though, in order to keep this from hurting your family situation.
Does that seem wrong?
Heck no! She betrayed your trust and friendship, why would you feel any different?
All I'm really trying to say is that you can detach because she's pathetic and is no real threat to you.