The Australia's Got Talent judge - who has 21-month-old son Ethan with the former professional rugby player - had been battling to save her four-year relationship since last May but after speaking to her older sibling about her romantic woes, she knew it was time to let go.
A source close to Dannii told Britain's Grazia magazine: "She's been understandably scared about splitting up, but Kylie reassured her that she was strong enough to go it alone and that her happiness should come first.VIDEO: THE MORNING SHOW - DANNII & KRIS SPLIT
"And in doing so it seems she gave Dannii the confidence to make the break."
After the split was announced, Dannii, 41, revealed she was planning to "retreat" for a few weeks to deal with the aftermath.
She wrote on twitter: "It brings me great sadness to tell you that Kris & I have separated. We still care for each other & ask for privacy at this difficult, in particular for our son Ethan who remains our number one priority."
Hours later, she added: "Hi Tweet peeps. Needing to retreat for a while. Thank you for your ever loving continued support. (sic)"
Kris added the pair had "love and respect" for each other but wanted some privacy following the end of their romance.He said: "Dannii and I have a deep mutual love and respect for each other and although things have not worked out we have a gorgeous son together that we both love and implore everyone to respect our privacy at this challenging time."