Hi hun, I feel for you and honestly don't know what to say. I agree with the girls in that you need to stand up for yourself and most of all Erik needs to be more direct with his mother too.
Bottom line this is YOURS and ERIKS wedding, no one elses. When it comes down to it no one else should matter (but unfortunaltley they always do). Who cares if its short notice?! If it's important to these people they will show up and if not, well it's not meant to be.
Either way i think your wedding will work out and everything will be unforgettable in a good way Keep your head up Andrea.... and tell the FMIL who the bride is. hehe