Message: Call to a member function email->from() on string

@Dave friend,

I am trying to ask what are the specific values that the from method is expecting.  It could be a case of wrong values that are causing the error.

The method CI_Email::from() accepts three arguments, all three are strings, the second and third arguments are optional. Read the docs. Nothing happens in the method that would produce the error described.

That error message would seem to indicate that the variable $this->email is a string and not an instance of the CI_Email class. How that occurs is not determinable in the code the OP provides.