It sounds to me like your fiance doesn’t believe that she is good enough as she is. You may not be a snob but she sounds very insecure. None of her lies are harmful. She isn’t stealing or cheating or manipulating you to do things you would find shameful. She is making herself seem just a bit more educated, a little younger, and with a background that is a little more successful in order to be worthy of someone like you.
What she doesn’t seem to understand is that you love her just as she is and that these adjustments of her story make you question whether there are other, more serious things she isn’t telling you. Her efforts to make herself more acceptable to you are now doing just the opposite. She is chipping away at your trust in what she says.
If you love this woman, then compassion, not anger is the solution. Angry confrontations about her “lies” won’t solve the problem. What she needs instead is to be reassured that you love her just the way she is. I hope she has enough self-esteem to be able to take that in and accept your love.
I wish you well.