The Wikipedia page you linked to doesn't make the claims that you are. It says that Babb volunteered for the FSA to help migrants, and that her supervisor Colli

The Wikipedia page you linked to doesn't make the claims that you are. It says that Babb volunteered for the FSA to help migrants, and that her supervisor Collins asked her to keep notes on her work there. Collins seems to have later shared the field work notes from her, as well as others, with Steinbeck when he was doing research. There's no claim that he read (or was even aware of) her manuscript, or that he dissuaded her work from being published (it says her publisher decided not to publish it after The Grapes of Wrath was successful). People can read the summaries of both if they like; there doesn't seem to be a lot of overlap other than they're both about downtrodden Okies trying to make it out West. Edit: Also worth noting that Steinbeck's nonfiction account of migrant workers in California, The Harvest Gypsies, was published two years before Babb began her volunteer work with the migrant farmers.