Yo, same with Eleanor in "The Haunting of Hill House". I felt that character to an absurd degree. Like I gasped out loud >!when she hit the tree and legit had to take a minute to make sure I was not dead.!<

Might be different for you, but what helped for me was talking walks in between reading sessions and just thinking about all the ways I wasn't her. Sometimes long, sometimes short, just around the block or to the corner store or walking the dog. No headphones, just thinking and moving. I believe more than anything the movement is what did the trick; like "I am physically moving away from the place where I experienced these emotions and am also mentally moving away from that headspace."