Coming to her aid is a babysitting, pot-smoking hitchhiker named Shaz (played by Toni Collette) who Barry Moochmore picks up and brings home to look after the family.
Hogan said this actually happened in his life and he is still in contact with the real Shaz.
He said his father would have been pleased with "his role" because he gets to redeem himself and is seen in a somewhat more favourable light than he was in Muriel's Wedding.
"My dad saw Muriel's Wedding surrounded by his mates and the only thing he said to me was 'that cut a bit close to the bone'," Hogan says.
"Then when the film became a hit he reversed completely and said 'I love that film, it totally vindicates me'.
"It was like he'd invented a new film in his mind and you'd think he'd been father of the year.
"When I made Muriel's Wedding that was a much harder portrait of my dad than this one because in Mental, Barry Moochmore redeems himself."
When Hogan wrote Muriel's Wedding he asked permission from his sister to tell her story.
This time he wrote Mental without the approval of his siblings, although they were not kept in the dark and often visited the set.
"They haven't seen the movie yet but the moment I showed up (for filming) they came out to the set a lot," Hogan said.
"My brother Thomas said 'what is he doing this time, another film about us' because Muriel's Wedding was autobiographical as well so they know what to expect from me."
Having drained two feature movies out of his family life, Hogan said there's unlikely to be a third.
However there is possibly one to be drawn from the real-life Shaz who is a pivotal character in Mental and has issues of her own.
He said she still pops up from time to time and there was one instance where Hogan and his wife, fellow filmmaker Jocelyn Moorehouse, had to ask her to move out of their Melbourne home.
"The real Shaz was in and out of my life for 20 years and I think that if anybody wanted a sequel for Mental I know exactly what Shaz goes on to do - she goes on to drive me crazy," Hogan said.
Movie profile
Who: PJ Hogan director
What: Mental starring Toni Colette
When: Opens in cinemas on Thursday.
- AAP