I've been hesitant to come out with this opinion, considering the popular sentiment on this board, but if you guys can forgive me for writing MFS fic you can forgive me for anything.
In the past Kermit and Piggy's relationship has irked me. The idea that someone can just claim someone else against their will and, by persistence and brute force, eventually get what they want ticks me off, to put it mildly. I won't go into why it pushes my buttons; that's personal stuff that doesn't need to be detailed here.
In my mind, love isn't won through persistence. You can't just grab someone, yell "Mine!" and expect to have your way. Love isn't won. It isn't earned. You can't demand it. It's given willingly or it's not real at all.
I believe that this movie portrays their relationship in the best way I've seen yet. Piggy had the nerve to fake a wedding to snare Kermit, and then build a home for them, presumably without his input. If I were Kermit, that would have been the last straw. But this time I could see something underneath Miss Piggy's overbearing attitude. Oz spoke of Piggy coming from pain, and I could see that here. She adores Kermit, and misses him, but she has no clue how to express it. She can't stand being seen as vulnerable. So she falls back on manipulation. She plays go-away-closer with Kermit, and even tries to fool herself into thinking she doesn't want him any longer, to bandage old wounds. Classic Piggy.
In my mind, she redeemed herself when she took over after Kermit gave up. She did what Kermit couldn't bring himself to do because he's too nice, and got a celebrity host no matter what it took. She pulled the Muppets together using her greatest asset: the moxie that she's shown from the very beginning. And I get the sense that she didn't do it as part of a plan to win Kermit back; at that moment it had become her mission as well. By the end, she was no longer trying to claim Kermit, and I got the feeling that perhaps they had gotten a lot out of their systems and could try it again, this time on a more mature, realistic level.
That's my opinion, anyway. The short version of it. This and a dollar will buy you a can of New Coke Zero.