First of all, 6 weeks to the wedding!! It came around so fast.
Can the dress maker accommodate her on the 22nd and have it done in time if it's just one more fitting? I would try that first to try and keep her happy. If not, tell her that she will either have to take the chance on the alterations being ok or get the dress to her in dublin and tell her to get them done herself.
I wouldn't worry about the shoes and clips etc. They will be so far from your mind on the day that you won't pass them a second though. I know is hard but I'd try not let it get to you.. You'll have them as your in laws forever so to keep the peace I would try to smile and nod and grit your teeth.
Deep breaths!! You'll have an amazing day.