Wedding dress errors

Hi all please help!
So I ordered my dress last January 2021. I was so happy it is my dream dress. I loved it so much I took the leap and splurged more than I originally had budgeted myself. For reference purposes the dress cost my almost $6,000. When the order was place I was measured up all over and had to have the sleeves made to fit my arms and also since the dress had so many layers of horse hair tulle they strongly suggested to have the manufacturer do the hem custom to my measurements. This would be at an additional cost of $587 which they offered to split that cost. I was also given the trunk show 10% off. When the dress arrived and I went for my first fitting none of the tailored measurements were done. The sleeves didn’t fit at all the hem was way too long. They took measurements again and sent it back to get redone. When it returned it was still not done sleeves still didn’t fit hem still not done at all. Fast forward after sending it back 3 times finally the sleeves fit although they are big now but they fit! But the hem was still too long. The owner of the bridal shop is now telling me I can have their seamstress bring up the hem they will refund me the cost of hem so I can take that to pay the seamstress. I asked them how much she would charge for the work she said it would be about 300, so I could take the 287 I would have paid the manufacturer and pay the seamstress and that she (the bridal shop) would cover the remainder amount of $15-20. I don’t know what I should do I am afraid to say yes cause once I pay and sign off on the dress and take it from the shop and have the seamstress make the alterations cause if she messes up there’s nothing I can do about.