One way to take it is that Tyrell is Elliot's dad, except younger than the Christian Slater version, like when he worked at Evil Corps. Joanna discusses giving birth to a girl and giving her up for adoption while talking about how much she loves her newborn son. This could refer to Darlene, and how she is absent from all of Elliot's childhood flashbacks. She also looks like Elliot's abusive mother. She seems to know Elliot when they talk, and looks like she may know about Elliot's mental illness, similar to Elliot's mother later in the finale in Time Square. Is Tyrell another manifestation of Mr. Robot? Possibly. Another way to take it is that they are all real people, just another couple repeating Elliot's childhood memories.