Kerry Katona's daughter needed counselling after she split from George Kay.
The Atomic Kitten singer separated from her third husband last October and 13-year-old Lilly - whose father is Kerry's first spouse Brian McFadden - found it hard to cope with both the separation and having no one to talk to about her mother's bipolar disorder, so sought professional help.
She said: "I had counselling when George left, he was my best friend. It was nice to have George because sometimes mum locked herself away in her room.
"It did help because it was nice to have someone who wasn't family who didn't know anything to talk to."
Lilly and her older sister, Molly, 14, admitted it can be "tough" dealing with the unpredictability of Kerry's mental illness but they understand it more now they are older.
Speaking on TV show 'Loose Women', Molly said: "She wants to do everything all at the same time. She goes crazy but in a good way ...
"It's a lot easier to talk about it now were older as we're independent. I'll get up in the morning and make the kids breakfast, because either mums busy or she having a bad day."
Lilly added: "When it's not a high...it can be really tough. When she's happy it can be really good like she took us to Brighton one day. It's mostly to do with the weather."
Kerry - who also has children Heidi, nine, and Max, eight, with second husband Mark Croft, and two-year-old Dylan-Jorge with George - was diagnosed with the condition when she was 25 after regularly being sent for "compassionate leave" when she began her career with Atomic Kitten.
And over the years, the 'Whole Again' singer has always been open with her children about her problems.
She said: "I used to lock myself away in my bedroom.
"As the girls have got older, and they've seen the stories written about me, I've been quite open and honest about my cocaine addiction, shown them the video [of me taking cocaine], which is also about depression and bipolar. You have highs and lows, there is nothing in between for me. It's all or nothing."
The 35-year-old star was "proud" of Lilly and Molly for making their first TV appearance, and hopes it will raise awareness of mental health issues.
She tearfully added: "My girls are here on national television. They've seen a lot and I'm so grateful they turned out amazing and I'm so proud of them.
"And they feel strong enough and confident enough to be here and raise awareness of this illness."