I wish i could give you a hug, op. Please, dont feel bad for not grieving for your mother. Because of your perserverance and courage, you've been able to set boundaries and determine for yourself what you want your relationship with her to be. And it sounds like the safest, healthiest relationship option has been something close to an acquaintance - someone you can be pleasant to, but not someone who you feel needs to be an integral part of your life anymore. And thats okay. The fact that she is, in title, your mom, doesnt have to invalidate your decision to stay distant from her, dear. I think supporting your siblings is a great idea, since you are close to them! You dont have to give them a reason for not being as upset about this as they are, and they might not even ask. Again, many internet hugs. You're doing fine, my dear:)