Apparently she is furious that three of the children born to her during her captivity in the cellar keep referring to Rosemarie, 69, as 'mother', Austrian media report.
Joseph sired seven children through his daughter. But the seventh one died and was promptly burnt in an incinerator by him, it is reported.
He moved three of his offspring through his daughter upstairs where they were brought up by him and Rosemarie. That the three should still keep calling their grandmother 'ma' proved galling for Elisabeth, it is said.
So peremptorily Elisabeth ordered her mother out. With no money, cut off from her family and with her 74-year-old husband in jail awaiting charges that might see him imprisoned for life, Rosemarie is said to be shattered. 'She has no idea where to go or what to do,' said a family friend.
The mother was moved into the psychiatric hospital with Elisabeth and the incest children after Fritzl's secret cellar was discovered in April this year.
Rosemarie returned to the dungeon house a month ago to collect toys and possessions from the cellar.
But she is reportedly too scared to live in the rambling 66-room house on her own, sealed as it is with police tape as a crime scene location and emptied of lodgers.
Doctors say that Rosemarie - married for 52 years to Fritzl even though he was imprisoned early on in their marriage for raping a nurse - is perhaps the most severely disturbed of all the family members.
There were reports recently that Josef Fritzl humiliated his wife at a swingers club by forcing her to watch him romp with another woman.
Builder Paul Stocker, 65 said: "An elderly couple came in, they looked just like an old pair you might see in a park feeding the pigeons.
"It was Fritzl and his wife. She went without a word to stand in the corner.
"He treated her like a dog. She had to sit in a corner and watch as he did stuff with a young woman."
It is reported that on reunion at the clinic, she told her pallid, prematurely aged Elisabeth, "I am so sorry...I had no idea."
But possibly Elisabeth is not convinced. After all her father had begun to abuse her when she was just 11 years old.
For all her reported helplessness, Rosemarie still remains a puzzle.
Questions stack up. Who then supplied the four prisoners with food in the cellar when Josef was away for weeks? Did anyone help at the births of Elisabeth's seven babies? In the event of Josef's death, would the cellar family have starved to death or had he covered this eventuality by drawing someone else into the web?
As a blogger remarked acidly, "Rosemarie Fritzl's alleged ignorance of the abuse suffered by their daughter seems incredible; given her husband's previous criminal record, the extraordinary stories he asked her to believe and the fact that he built the basement cell under her nose and kept his secret family there for 24 years.
If Joseph was sexually molesting his daughter since she was 11 years old, did not Mrs. Fritzl see a change in her daughter's behavior?
And there were so many signs, that she could have picked up:-
The construction of the sound-proof basement beneath the family home was completed while the family was living there. Surely Mrs. Fritzl would have seen mess being created with the soil being moved or seen deliveries of plumbing supplies, tiles, cement, trades people arriving to install appliances or fittings. Would she not have asked, 'Honey, what is all this work in anticipation of?' Or 'What are you building?' She would have noticed the construction process. On completion of the Basement, the daughter suddenly goes missing.
The enormous food bill required to feed a further 4 people per week.
The unusual behavior patterns of Fritzl. He would disappear to the basement for hours, sometimes even for days.
The three children that Josef bought upstairs to be looked after by Mrs. Fritzl, arrived separately and each time Rosemary happened not to be at home.
Rosemarie's suspicions not aroused at all?
Living with a tyrannical man like Josef Fritzl would have been an awful experience and one could sympathize with Mrs. Fritzl, but how could she remain anesthetized to her surroundings?
Perhaps it is such questions that are haunting the entire Fritzl brood now. And Rosemarie would have to clarify. She cannot afford to take cover under her alleged subservience to her monster husband.
But there is this other view. Misplaced loyalty, fear or self-deception allow all kinds of women - from battered wives to partners of paedophiles - to suspend disbelief. In effect, not to question.
To some wives, a husband can simply do no wrong, whether he is a philanderer, a violent drunk, a spy - or a murderer, even when evidence mounts up to the contrary. Rosemarie Fritzl, "the perfect grandmother", may simply demonstrate an extreme form of what therapists call cognitive dissonance.
Incredible though it may seem, psychologists agree it is possible that she refused to question her husband about his strange absences. Very likely abused and tyrannised herself, she may have reached a point where the only response to each implausible story was denial.
"It is perfectly feasible that she did not know," says Dr William Conn, an expert in child abuse and neglect. "Living with a tyrant who exercises immense control eventually prevents the dependent partner from being able to process the information or challenge anything. Challenge ceases to be an option."