The solo pop singer and Celebrity Masterchef winner revealed that she would always look out for Katona because of their interlinked pasts.
"She's going through a hard time," she told the Daily Star. "Kerry taught me a lot of stuff, some good and some crazy.
"We have gone through a lot. She knows if she wants me I'm there for her."
McClarnon, 28, releases a new single 'Lately' on May 18.
Katona's private life has been the centre of tabloid speculation in recent weeks, with stories alleging that the reality TV star was having problems with her finances, husband Mark Croft and drug addictions.