On page 28, Ehrenreich discusses her difficulties in making enough money to meet all her expenses, including her rent.
On page 41, Ehrenreich discusses her "slide into poverty" as a result of failing to make ends meet.
On page 185, Ehrenreich discusses her repeated failure to find cheaper places to stay during the time that she works at Walmart.
Here are a couple of interesting stories that might help with your thesis.
Charles Platt, novelist, worked at a Wal-Mart and had a very different experience; in particular, he mentions that he was constantly reminded to take his breaks.
Matthew Pulley, UNC student, lived in a very similar situation and believes that Ehrenreich "set herself up for failure," and so her book was a self-fulfilling prophecy.
#2 is right, in my opinion - I don't think she "failed" in any of her positions. She demonstrated the difficulty of trying to survive under lower working class economic conditions, which ultimately proved not possible for her experiments. That was because she had the luxury of being able to walk away and return to her "real life" situation as an individual not solely dependent on minimum wage / no insurance employment.