Fiancee said she doesn't want to get married, Where do i go from here? Advice?

I am 29 and have been with my fiancee for 8yrs, engaged for 2, she is 26 and gave birth to our first child 7mths ago. She was diagnosed with borderline personality disorder when she was 19 and after our sons birth she suffered from postnatal depression, I am a full time firefighter and because of shift hours i cant always been there. Her family are very dysfunctional and many of them have broken marriages and drink problems, she is the youngest of 7 siblings. Previous to proposing to her she told me she didn't believe in marriage as she had seen so many fail and she didn't want to deal with that, shes convinced her family are jinxed when it comes to happy ever afters, Despite that she agreed to get married as she knows how much it means to me to marry her. We don't have a date set but last night she told me she cant to the marriage thing and is petrified of having a wedding. I feel so let down i love her to death and cant imagine my life without her but i really want to make her my wife. When our son cries she always says she has to do something -bathroom, phone, shop etc- she hasn't got a bond with him at all and will try hard to avoid being around him alone, she works full time so as both her parents have ped away my mom or sisters look after him while we are working. She was always the life and soul where every she was and has so many friends but now she just daydreams a lot & doesn't bond with our son. I feel l ike im losing the woman although we are still together, Any advice on how i handle any of this would be great.