The actress, who walked down the aisle in September (12), was a wreck after putting her all into the stage show adaptation, in which she plays tragic prostitute Fantine, and insists it was Shulman who boosted her spirits when the production wrapped.
She tells Vogue magazine, "I was in such a state of deprivation - physical and emotional. When I got home, I couldn't react to the chaos of the world without being overwhelmed. It took me weeks till I felt like myself again.
"The first time I really threw everything into a part, which was when I did (2008 drama) Rachel Getting Married, there was no one waiting for me when I got back. This time, Adam was there. He gets what I do and who I am and supports me in it, and that's pretty awesome."
Hathaway ate just two squares of dried oatmeal paste a day to lose 25 pounds (11.3 kilograms) and look painfully thin onscreen, and admits the drastic diet tested her strength.
She adds, "I had to be obsessive about it - the idea was to look near death. Looking back on the whole experience - and I don't judge it in any way - it was definitely a little nuts. It was definitely a break with reality, but I think that's who Fantine is anyway."