How come people say that my fiancee will be disappointed because I did not have the job I say I will have?

So my parents and I told my vietnamese fiancee that I was studying pharmaceutical technology in The University of California San Jose Area which I would have a job as a pharmacist. Now I'm not doing well in college and I got suspended and kicked out of college now since I functioned poorly. Now I work at the mcdonalds restaurant in San Jose and people say my fiancee is going to be disappointed in me. They said her and her family will be extremely disappointed and they said if she still wants to marry me then she is doing so just to get a ticket to the united states. Why do they think she will use me now because I work at mcdonalds ???