PLEASE READ!!! Mother and Fiancee started hating each other after I lost my dad?

I have a dilemma on my hands. In February of last year, my world changed, my 55 year old father died suddenly of a severe stroke at work. During that time my fiancee's family played host for a week to my mom, stepdad, and sisters ( who had moved down to Florida in 2002, while I chose to stay up in NY and finish college and live on my own ) During that week, stress was at an all time high. My fiancee and I live in NYC, and are very close with her family because they live so close. My family lives in Florida and is up in NY for 4 days, at most, once a year. Because of the stress of losing my dad suddenly, trying to arrange funeral plans, and try to console my teenage sisters, I felt like I was on a roller coaster. My mom, whom I love more than anything,is a "bleeding heart", she will tell her life story to anyone that will listen, including divulging private family information that really should not be told to people they have only met 2 or 3 times. My mother, unbeknownst to me, spoke a lot about my family problems, her divorce with my father, and her financial and credit problems in the past. My fiancee's family is to stereotypical "All-American" Ozzie and Harriet family. Everyone gets along, and both parents have fantastic relationships with each other and the kids. Suffice to say.....after that week, my fiancee and her mom withdrew from talking to my mother on Facebook and stopped asking about my family from time to time ( before my dad died, it seemed like my mother, my fiancee and her mom, were really hitting it off) Last week , my mother came up to visit, it was the first time I had seen her since the funeral. I was excited to see her,however, my girlfriend was very reluctant to go out, and socialize with my mother, but ended up still going out with me to visit my mom , but was extremely quiet at dinner. Today ,my mother called me to tell me that I should "reconsider getting married, and plain and simple, doesn't like my fiancee at all. I think it's because my mother really hasn't had a chance to et to know her How do I handle this????