The problem with this is most Pyrrhas will not use many punishable attacks. For example, 66A, 88A, 66B, BB, AA, 88K, 3B (at range), 6B+K, 4K, and 66A+B are all not punishable. This leaves only 1K, which is very risky to duck, and 236B, which will likely not be used unless it hits. Also, I think Pyrrha can stab punish after the first hit in 6KBK. However, I can see this as being a way to bait a stab.
My theory is, whiff punishing should be the thing to do against Pyrrha. Most of her moves have shorter range than Ivy's, so you should be staying just outside of her reach. When one of her moves whiffs, use 6B for speed, 88 for damage, or 2B+K for range. Don't be afraid to backdash, since her most damaging way to kill backstep is with a stab, which is very risky to use out of the blue. Don't sidestep much against Pyrrha because of her 1K and 66A. Pyrrha does not do much guard damage with her non-punishable moves, so you don't have to worry about guarding too much. The main difficulty with this is just being patient enough to look for an opening. If anyone disagrees with this, I'd appreciate a second opinion.