Reddit user Marty5151 suggests that the "her" that Toby is referring to on the phone is most likely Kate. Clearly, something has happened between the two of them — like perhaps a divorce (or worse). If Randall is rallying the entire family, he may believe that Kate will need Toby's support, even though Toby isn't so sure about that. That means that while Randall and Toby are talking about one "her," Randall and Tess could be talking about another person entirely, someone who the entire family is intimately connected to.