"I want to bake a cake for Miranda," Jenny announces to Emma once they've left the other girls' earshot. "There's kitchens here, right? Would they let me bake, do you think?"
Emma supposes that they might, but has no idea where the kitchens are, so Jenny flounces off to find an older Hufflepuff to ask. The girl she asks for directions takes this very seriously, writing them out carefully step by step for her before handing it over. When asked about permission for baking, the older girl shrugs and says "the house elves probably won't care, just ask," which then dovetails into a conversation explaining house elves, but eventually Jenny thinks she has some idea what she's doing and heads for the kitchens.
Thanks to the extremely comprehensive directions, Jenny finds the kitchen immediately with no trouble. Convincing the house elves in the kitchen that yes, she's been cooking for years, no, she is not going to try anything fancy, and yes, she will stay out of their way, takes a little longer. She eventually charms them into it with protestations of "but it's for my friend's birthday!" A couple of them are even lured into helping her, which means the cake ends up decorated rather more nicely than Jenny could have managed by herself. Since the cake is chocolate- she had to guess on flavors, but she's seen Miranda eat a Chocolate Frog and really, who doesn't like chocolate?- she proclaims that 'close enough' to bronze and frosts the rest of the cake in blue, with her new elf cooking companions providing fancy little flowers along the border and chocolate sprinkles as extra frills.
She is extremely pleased with the result! She heads back to the Hufflepuff common room to fetch Emma, looking like she would be skipping if only she wasn't carrying a cake, and they head to the library to meet their friends.
"I'm glad! I had to sorta guess, I don't have dessert with you that much, but chocolate seemed safe!"
"I approve this choice!" Emma says happily, digging in. "Happy birthday again, Miranda."
"Also, not literally puppy eyes. I tried that once. Not as cute as I was hoping."
She demonstrates. It is extremely pitiful looking.
"What? Nooo! You get to see your family! Hugs and Christmas and carols and stuff! It's exciting!"
"We aren't allowed to use magic outside school till we're of age," Miranda tells her. "Did you not hear that?"
"I knoooooow," Jenny says with a pout, "but I miss my family! And I don't really need to make flowerly purple stuff for a week anyway." She then pauses. "Um, does my hair stuff count? If it does it by itself I can't help it!"
"I don't thiiiiink Metamorphmagus things count. Actually, I'm not even sure if potions count, but anything with a wand does."
"I'm pretty sure only wands count. Accidental magic doesn't, and Metamorphmagus should count as that?"
"But only some of the morphing is accidental. That's a silly category if it counts as accidental."
"Well, anyway, she probably won't get an owl from the Ministry about it unless she does it in front of Muggles besides her immediate family."
"The Ministry has more to worry about than a kid shifting in front of her little sister, anyway."
"Okay," Jenny says, sounding more cheerful. "So, Miranda, whatcha doing for the rest of the day?"
"I thought maybe I'd borrow a school broom and fly around. Maybe see if I can teach Amber to play tag."