I take it that the author herself also came to the US as a teen, so this book would be a "How I tried to live the American dream" sort of thing?

I don't know whether there is a market for that in the US (I don't have any idea what the market for non-fiction is like in the US, i.e. what kind of books sell.), but if she wants to publish in any other way than self-publish, she has to think about who wants to buy such a book. Many publishers / agents request that you also say something about the possible market in the cover letter. By the way: want to buy is not the same group of people as "need to read". I've seen several application letters that pointed out who needed to read the book. (Usually everyone with a certain prejudice. Funny enough, those are the people least likely to actually buy the book.)

Her market could be people who want to know how immigrants become successful (or not). That may just be other immigrants and the odd sociologist studying the subject and looking for narrative experience.

90,000 isn't long for a novel. It would come out at about 260-280 pages. I'm sure she would be able to find a good editor if she was willing to pay for one. (She should look for one that also knows her native language, so the editor isn't too puzzled by some of the mistakes made.)