Anger, if not responded to, becomes rage, and then it becomes hate.
If you have anger and resentment toward your birth mother, I think it's OK to express that. If there's something you want to get off your chest, I think you should, don't worry that it is inappropriate. She may actually experience relief that there's an opportunity to have a conversation with you about what happened, and what she did, and the whys - even if you interpret them as excuses, she may see them as reasons.
Happy Easter and Passover.
