1: God forbid is a set expression, meaning "let's hope God won't let it happen!". It's used ironically here.
2: She's talking about a party.
3: If you have problems / are in dire straits...
6: She made a good "trade", so to speak, in changing boyfriend/husband
7: no offence means "don't get offended", none taken means "It's ok".
9: to screw is somwhat similar to f*ck.