I ask this question nicely. Why is a grown woman who has brought up children of her own, worrying about the vagaries of behaviour of an 8 month old baby. She is the person in charge and presumably has years of experience with young children, so should surely dealing with this 'problem', if 'problem' there is, with a shrug of the shoulders and a hug and a kiss.
My grandson, once on his feet had no time for me, he had 2 grandma's, so the one who he saw less of (me) was merely a spare, if the other grandma was not around, but DH was his grandpa and the only one he had, and he would, when we arrived, swerve round me to get to his grandpa. This went on for over a year. I cannot say it troubled me much, and of course something happened, he changed his mind and I became someone he was delighted to see. He is 14 now and we get on like a house on fire.
Children are like that, come to that so are many adults.