Ariel told Blair to help tell her mom that she's leaving with Vick's family today which Blair refused to do, that was before Flora found out Ariel was no longer in the pack house with them. If she had known about it earlier, she would have struggled to stop Ariel from leaving but at the same time.
She was trying to stop her baby Alpha and his crazy thoughts of Tiara possibly being alive.
"She asked me to let you know she's leaving because she didn't have the heart to do it herself, which I refused to do. We both had a little argument but she still wanted us to have one last hug, I stupidly refused to accept. Now I think I'm regretting why I didn't do it, I should have just done it. It was Ariel that wanted a hug, not just anyone"
Just like Blair thought before, it is finally coming to pass. She's starting to regret not giving Ariel the one last hug she wanted from her.