The mother of children's author Helen Bailey became "uneasy" about the man accused of killing her in the weeks before she disappeared, a court has heard.
Ian Stewart, 56, of Baldock Road, Royston, Hertfordshire, is accused of murdering the writer after plying her with sedatives in a financially motivated plot last year.
Her tearful mother, Eileen Bailey, told his trial at St Albans Crown Court that her daughter "panicked" about her deteriorating state of mind and repeated forgetful incidents.
She had become "highly anxious" and felt "spaced out" all the time, jurors were told.
Asked about her views on the couple's relationship, her mother said: "Well, I felt uneasy about it, latterly I was quite unhappy - mainly because of Helen's state of mind."
Stewart denies charges of murder, preventing a lawful burial, fraud and three counts of perverting the course of justice.
In the weeks before Ms Bailey vanished, she confided in her mother about inadvertently leaving her dog on the beach, taking an item scanner from a supermarket and not being able to recognise her hands on a computer keyboard.
Speaking to the court via video-link, with a framed picture of the author visible behind her shoulder, Mrs Bailey told the court: "That really worried me."
She added: "She just had such a good memory beforehand."
A week before her alleged murder, the 51-year-old phoned her mother, deeply worried after falling asleep for five hours - despite having a full night's rest.
Mrs Bailey said: "I picked the phone up and she said 'Hi Mum, it's me' and I said 'Hello you' and then, in this panicked voice, she said 'I just slept five hours'.
"That took me by surprise and I said 'You must have needed it' and she said 'What, after a night's sleep?'"
Breaking down, her mother added: "I feel I was dismissive."
She told the court she thought Stewart had cooked her daughter breakfast that morning, but on cross-examination said she could not be sure.
Three months after she vanished, Ms Bailey's body was discovered in a cesspit below the couple's sprawling home, alongside her dog Boris.
Discovered in her system during a post-mortem examination were traces of an anti-insomnia drug prescribed to Stewart, the court has previously heard.
Episodes of dizziness and tiredness were also reported to Mrs Bailey by her daughter about a month before she went missing in April 2016.
She told the court: "Particularly when she was shopping and wanting to reach up for something from the shelf - she would fall to the floor.
"I suggested she went to the doctor's."
Ms Bailey was said to have forgotten her beloved dachshund several weeks later.
Her mother said: "She said that she had come away from the beach and gone home and Ian had said he would go and get the dog, but she was almost traumatised by that, repeating 'You know, Mum, I would never have done that'."
In the wake of his fiancee's disappearance, Stewart behaved in an erratic and "rude" manner, jurors were told.
Detective Constable Hollie Daines said the defendant had told them that he "must be" a suspect.
She told the trial: "I found his behaviour generally quite unexpected at times - he had already snapped at me a couple of times when I was asking him to do an interview."
She added: "I found him rude, temperamental, unco-operative and dismissive of us."
After officers had concluded a first interview with Stewart, he is alleged to have said: "Am I still a suspect? I must be, I must be a suspect."
Jurors were also told the defendant had vetoed the idea of holding a press conference to appeal directly to his missing bride-to-be.
DC Daines said: "He wasn't keen on the idea, he felt that the media will twist anything he said and 'no' soon would end up being a 'yes'."