Wow.. that is truly a stressful story. and with the breakin even moreso! You poor thing!!!!!
I think you need to call her and just let her know how you are feeling. Perhaps start off by saying how you value her friendship and that after 8 years you would hope that a stressful situation wouldn't ruin it.
Let her know that you would like for her and her BF to make it to the wedding, but if they cannot confirm for you at that time, then you will be making the very hard decision of inviting a family member who you had been holding back on inviting in order to have them there.
I'm sure no matter what you say to her, from the sounds of it she's going to be a little bit difficult. Just brace yourself before the call... and do "ala Martin Lawrence" in badboys.... "Woooosahhhhhh" "Wooooosahhhhhhhhhh" "Woooooooooooossaaaaaaaaaaaaahhhhhhhhhh"
*HUGS* I hope everything works out for you so that you don't have any more stress!!!!