I've been thinking a lot about the PP system lately, and people's reactions to it, so I am going to dump a little blog here. This is all my opinion and analysis, and in no way represents the opinions of Peppy, or the community. It is only what I see happening.
The community has a double standard about Farming vs Skill. On the one hand they believe that a person can manipulate a ranking system to generate better numbers, and thus appear to be a good player when they truly are not. On the other hand they think that a person's Skill should be able to be proven tangibly by doing Skillful things.
So we have a problem here... Any system that measures a player's performance in some way will be vulnerable to attack, because it will be claimed that people are Farming it (manipulating the numbers). However, we still need a system, because we want to be able to show how skilled we are, and "win" at the game, in the sense of succeeding in some measurable way.
So what do we do!? Well, Peppy gave us the answer... He made a system that is so complex that it is impossible for us to completely understand it. To further obfuscate things, he has not released all of the information on how the system works. This is an attempt to appease both sides of the community. On the one hand, the system is able to measure us, so we can use it to express our skill. On the other hand, it's so impossible to understand that it cannot easily be manipulated, and thus it is difficult to claim that Farming is spoiling the system.
It sounds like he's solved the problem right? Unfortunately no... there is still a problem. The problem now is that we have a system which we can't exactly "win" at, because we don't really know how. Farming is stunted by making it unclear how to get better numbers, but "winning", which is very closely related to farming because it deals with manipulating a system in your better interest, is also stunted by being called into doubt and made hard to understand. This means that we can't be clear on how to gain Skill, and we can't be clear about what is really Skill and what is possibly a new kind of Farming.
That said, the new PP system does seem to deliver a decent value for measuring Skill, despite its difficulty as a guideline for gaining Skill. It may be that your inactivity for so long has caused the PP system to have to do calculations based on very little information, and thus you have risen far above your equally skilled friend. The system is based on placements in individual maps, so it may be that you have some placements that happened to look better than her placements, or she just hasn't placed as many times as you have recently since beginning to play again. He old scores won't make any difference, so if she isn't making new ones, then it won't show in her PP. At least that's how I understand it.