The Oscar-winning star has been shooting his role as the former US president in the biographical drama - due for release in 2012 - opposite Sally Field as his screen wife Mary Todd.
" Daniel Day-Lewis is extraordinary; I think he may be one of the best actors ever that we've worked with," she told Collider.
"We're about three quarters of the way through and it's been amazing, I mean he is really quite remarkable. Every day you get the chills thinking that Lincoln is sitting there right in front of you."
Kathleen, who is co-producing the film with long-time collaborator Steven, said Daniel doesn't stay in character all the time.
"He is very much deeply invested and immersed throughout the day when he's in character, but he's very accessible at the end of the day, once he can step outside of it and not feel that - I mean he's given huge scenes with massive amounts of dialogue and he needs to stay in character, it's a very, very performance-driven movie. But at the end of the day he's Daniel," she explained.