it's appears to be a replica tailored for her.
Notice how around the collar, there is different jewellery. On top of that, the diamond is much closer to the centre than it is on Michael and talking about the centre, the buttons are now (bigger) diamonds. In addition, there are red dots on the sleeve that don't appear to be on Michael's jacket:
Lady Gaga has an extremely high appreciation for Michael's fashion and maintains his clothes in a temperature controlled room so they are appropriately preserved. She would not alter Michael's clothing. Given she would have the exact jacket in her possession (assuming she owns it), she would be able to create a very close 1:1 replica with extra specifications she desires.