One person close to me is also currently still in the process of unraveling the failure of bonding with her mother with the help of a therapist. Failure from the mother's side. The things she internalized and have plagued her ever since turned out to be quite heavy. She at least had the comparison with another, later child as an anchor point to know that it doesn't have to be this way. (As a child she assumed this is normal.) It's certainly a lot of trauma to process, but I'm glad she's doing it after all, she carried that around for decades. That's long enough to say the least.