Fiona is a proficient liar and very secretive, her entire life over 30 years has been a lie.
Lying over the death of her father and lying about being raised by foster parents. There has been no mention of her mum but on the headstone of her grave it said she died 11 years before Fiona's father, she admitted to her children she was 20 when her father actually died so she would have been 9 when her mother died. She had said to her husband in Episode 1 that she had not known either of her parents. She said "one" of her reasons for lying was she didn't want them to see the gravestone and find out that he was a policeman so it suggests there were other reasons too.
Not telling her children or partner she was in the police. Not telling her partner about her battle with alcoholism and that she had depression and had tried to take her own life on two previous occasions. Not telling him she was responsible for the death of a child.
When in the counselling session with the young woman her speech on what lying does to people close to you was poignant. Her explanation on how it destroys trust and stops people knowing you and understanding you so they are unable to help you when you are struggling.
When she went to see her partners brother about stopping the loan or changing her surname on the loan application he asked what would she do for him in return? She was next seen driving home crying. What did he suggest in exchange for his help? It appears she didn't do anything as her partners brother phoned next day to tell her partner.
When she tells her partner about the car accident that resulted in her being responsible for the death of a child she actually shifts the blame. She suggests the other car was on the wrong side or the road and that the child was not properly fastened into the car seat. Even though convicted she still says she doesn't think it was her fault. There is no mention to he partner that she may have been drink driving.
Fiona has been practicing as as therapist without a licence for 16 years. That is a massive risk to take.
She was keen to repeat that she thought Walsh death was and accident (did she accidentally kill him?) and seemed eager to shift the blame. She told Cassie that it was all of the other suspects who put the body in the car it wasn't her as she was in too much of a state (just like the state she was in when police couldn't take a breath test off her years later?)
Re pen use: Dean, Fiona and Liz are right handed and Ram is left handed. If pen was inserted when face to face it would suggest a left handed person but if it was from behind then likely a right handed person.