And then the dad king said, "Hey, it's not enough that my sons have to marry girls that they basically catch with their arrows, let's make it a True Test Of Woman Skills, so make me a shirt." And the prince was very sad and his amphibian wife was like, "Dude, chill, just leave me to it, you'll have it in the morning." As soon as he left, she kicked off her frog skin and called for her servants, because OBVIOUSLY, you can't do that without help and made a lovely shirt and it was the Best. Shirt. Ever and the other wives were jealous, and the king didn't help matters much by saying, "Um, you guys suck and Froggy is my favourite" because I think we're establishing that he was a really good parent.
And then the king was all, "I'm going to have a party and your wives had better be presentable" and the other two princes were all, "SCORE!" because they had trophy wives and what is housekeeping but an old fashioned accomplishment and a man needs a wife who is perfect in the kitchen AND the drawing room. So the prince was very sad and his frog said, "Chill, I'll come, but I'll be a bit late, and the thunder will be my chariot" and then at the party there was thunder and lo and behold, the frog was actually a lovely lady and everyone at the party said, "Your wife's HOT" and the other two princesses, fearing for the slim foothold they had in that household, decided to do as she did, which was put chicken bones up one sleeve and dregs of wine up another.
But when she waved her sleeves, a stream came out of one and swans came out of the other, whereas the sisters-in-law just got their bones and wine in the king's face and he sent them out and their husbands were really pissed and they probably had really bad marriages afterwards, but we don't know because that's where their story ends.
But the prince ran back into the bedroom and saw the froggy skin where she had discarded it and was like, "FUCK inner beauty" and tossed it in the fire because no one had ever taught him that a woman's body belonged to her alone and it was not for him to burn her frogginess, it was her choice, entirely.
So the frog-lady came back and said, "OMG, what have you done? In three days, I would've been seventeen, and we could have been married sans frog and now I have to go and live out my curse because I was cleverer than my dad and he couldn't bear it and cursed me, so goodbye forever."
To rescue her, the prince had to prove he was a good person by not killing animals who rewarded him for NOT killing them by helping him out and then she was free, and probably learned how to be a bit stupid when talking to men so that the curse was never put on her again, because this is how we teach women that being too smart can be bad for you.