My girls want nothing to do with each other

My girls are teen and tween age and they were so close when they were little.  They played together, snuggled together, my oldest would feed the younger one and sometimes read to her.  They were so happy.  And then they weren’t.

My older one became resentful and unhappy and pushed the younger one away. The younger one was so hurt and confused and often cried and cried about it. Nothing I did worked; it just seemed to make it worse.

Now neither one of them even remembers the time when they were happy and close.  They only remember the resentment and anger and hurt.  My older one recently tried to reach out to my younger one and was rejected.  The younger one feels totally justified.  My older one is now the one confused and hurt.

As a mother, this is a nightmare.  It causes me so much pain and hurt because they are hurting.  And also because I think I could have done something differently and prevented this.  I have a big influence on them and it’s not the same as other relationships.  My words and actions do matter to them and shape the way they see the world.  I didn’t understand the responsibility I had in teaching them to love each other and now I feel it’s too late.  This is a guilt and pain that I can’t shake. I live with it every day and I don’t know how to get past it.