I'm so sorry... I had a betta that had fin rot almost his whole life, no matter what I did. He finally died of columnaris. I gave him so much antibiotics his whole life that he finally got a real bad infection at the end and it just was too much for him. But if I didn't give him the meds, he would have died a lot sooner.
I think you did the right thing by continuing to treat Pinky. That's 2 or 3 months more that she had with you! I remember the pics you posted before, and one of them did look like she was getting better, so I'm sorry to hear that she didn't make it.