The video she posted appeared to have been taken back in 2015. It included Eileen along with their Y&R costar Amelia Heinle.
Kristoff, Eileen and Amelia all promoted a then upcoming Y&R fan club dinner in the footage. Amelia jumped into Kristoff's arms while Eileen locked arms with him.
She posted the clip before Y&R aired a special tribute to Kristoff on Friday, February 8.
Eileen has been one of many Y&R costars to talk publicly about Kristoff's passing over the past week. The 52-year-old died on Sunday, February 3. His cause of death has not yet been determined.
Others who have shared kind words about their late friend included Shemar Moore, Eric Braeden and Melody Thomas Scott.
The Talk host Sheryl Underwood broke down while discussing Kristoff on Monday, February 4.