How to not sound like a bitch when I say this?

My dads a drug addict. My mom suggested he leave the house and get help, he refused then on his own agreed to move in with my aunt and seek outpatient. He hasn’t gone and is still at my aunts.

We hired an interventionist and picked a date. My aunt then called off the intervention citing that my dad had a work project due and wouldn’t go. We chose a different date after the work project due date.

This time she ignored all emails from the interventionist and sent an email 3 days before the supposed intervention basically being like “does this still work?” Then asking if my uncle had confirmation from my dad that they were meeting(they’re going to meet and we’re going to come and do an intervention). Then a second email is sent out essentially being like that date doesn’t work for the interventionist.

I’m supposed to move to another state 3 hours from home and me and my fiancé basically pushed our move back to accommodate this intervention that is now rescheduled for when we’ve already moved.

I’m pretty pissed that it’s rescheduled and want to tell her that we pushed our move back for it and I’d try to make the rescheduled date but probably can’t go. I don’t want to sound too not just though. Advice?