If you look at Ehrenrich's conversations with Gail, you can see the mix of the insider and outsider at its most obvious. As a fellow employee, they can complain about similar things and have some common ground. But when Gail suggests that she will move out of her current living situation to get a room at the Day's Inn, Ehrenreich's status as an outsider takes over.
She can point out to Gail how dangerous that is and the fact that it really is far from ideal, but she also cannot fully empathize with Gail because she always has the option of returning to her "other Barbara" or falling back on resources that her co-workers never imagine. The fact that she is never fully immersed in the experiment because of this fall-back option creates problematic moments.
Ehrenreich addresses this, at least partially, when she returns to her other life briefly and notes that she feels alienated from her previous lifestyle. This is of course a nice observation but in the end does little to truly embed her in the experiment that she sets out to undertake given that she never has to face the fear of really losing her job and running out of money.