In most states (and I believe in all states, during the time period in question), only single people or married couples can adopt a child, so it would not have been possible for the second mother to adopt (unless the first one gave up her legal rights to the child). I seriously doubt Clark's assertion that McLeod never wanted to adopt -- the facts suggest she simply wasn't legally able to.
At any point in the past seven years, this woman could have requested and been granted custody. She didn't.
Dr. Clark said the room-mate never wanted custody of the child, and the facts support this statement.