After disengagment with all my adult SK's for a number of years I now have a nice relationship with SD1 (not the rest).  She is married with kids of her own and when I stopped chasing her and trying to make a relationship with her she came back and has put some effort into our relationship.  Her kids call me grandma and I enjoy them a lot.  It is a nice relationship with both SD1 and the kids although it is not all that close.  We talk once or twice a month and she comes to visit 5 times a year for an overnight.  

Now for the issue.  SD1 (now 35) has never cared for my BD (now 29), from a different relationship. SD was a total bully when she was a teenager and BD did not talk to her once she went away to college.  In recent years, BD has, on several occasions to reached out to SD1 and tried to connect.  Both are married, have young kids, at similar life stages and BD has felt it was time to move forward.  Each time it would go good for a while and then SD1 would get upset about something and would blow a fit.  It was always about something stupid and trivial that involved SD1 being unhappy over being ignored, not asked, not chased, not begged, or not doing "it" her way (whatever "it" was).   I have given BD credit for reaching out time after time.  Not once has SD1 reached out to BD to try to fix the relationship.  But I think the last SD fit was too much to take and BD is ready to be done - forever.  The event this time was because they both have children with February birthdays that are 2 days apart.  SD1 was unhappy that the only day that worked for family parties was the same day for both boy's.  Not sure why she was unhappy since SD1 has NEVER invited BD to a birthday party for her son and the kid just turned 9.  Just have your separate parties like always.  

I have to be supportive of the disengagement.  After all, I have been there and done that.  I respect her decision to say "no more".  However, I don't kow how to be the person respecting the disengagment.  What do I say anythig when SD1 asks why she is not included in the housewarming party, the 4th of July picnic? or the trip to the zoo?  When I have an event do I ask both of them and let them work it out on their own?  Do I try to schedule events with just my BD and her family?  And then have separate events with SD1?

Help!