Permanent solution
Our tale begins in an abandoned classroom at Hogwarts. The Fat Lady is being visited by her boyfriend, Ernie.
The Fat Lady said, "You look awfully happy today, Ern."
Ernie asked, "Do you remember when I stole that girl's corpse for you to try out?"
The Fat Lady smiled slightly. "That was the best day of my life."
Ernie beamed, "Well, after that corpse went past its sell by date, I have been looking for a permanent solution for you."
The Fat Lady guessed, "You found one?"
Ernie grinned. "I did! A potion to be exact."
The Fat Lady pointed out, "I can't drink potions."
Ernie told her, "I even thought of that, Bern."
He produced a piece of paper that had a picture of a potion on it, and stuck it onto her portrait with Spellotape.
The Fat Lady gasped. "You did all of this for me?"
Ernie nodded and replied, "Of course, I would do anything to touch you properly again."
The Fat Lady picked the potion up and drank it.
After several tense moments, she stepped out of her frame.
Ernie pulled her into a hug and whispered, "I love you."
The Fat Lady responded, "I love you too."