I don't know if this is what you wanted but I hope you like it. I watched a horror movie and came up with this.
It was Halloween, the favourite time of year for all Death Eaters and ex-Death Eaters alike, including Bellatrix Black. She and Hermione had just been at a Halloween party that the Potter's had hosted.
It had been slightly awkward at first given Bellatrix's past, but Harry had done his best to include them both. As the night had gone on, the awkwardness faded letting everyone have a good time.
Eventually the party winded down and people had started to leave. Hermione and Bellatrix said goodbye to Harry and Ginny and left. They decided to walk the short distance home, as neither trusted their judgment to apparate after drinking.
On their way home they went past an old building rumoured to be haunted. "Let's go check it out" Bellatrix suggested.
"It's just a haunted house Bella. There were plenty of ghosts at Hogwarts" Hermione protested.
"But not this one. This one is supposed to be even scarier than the Bloody Barren."
''All the more reason not to go in there."
"Please 'Mione?" Bellatrix pouted at her girlfriend of two years. "I thought you Gryffindors were supposed to be brave."
"Brave yes, but not stupid. Who knows what is really in there? We could be in a lot of danger."
"I'll protect you. I won't let anything happen to you." Bellatrix captured Hermione's lips in a chaste kiss.
"Fine, we'll go in." Bellatrix let out a noise of excitement and led the way to the front door. As they went through the abandoned house, there was an odd chill in the air. It felt unnatural.
They went into every room trying to find clues as to whether there was a ghost in the house. When they made their way up the stairs, things started to get really spooky. Loud bangs came from all around them, objects like books were thrown at them. Which they deflected with their wands. Finally they reached the last bedroom in the house. Bellatrix tried to open it but it was locked.
"Alohamora." Bellatrix cast the unlocking charm, but it didn't work.
"Bombarda!" Hermione blasted the door open. Inside was a child's bedroom, a bed was against the far wall and toys littered the floor. A young girl sat on the bed, legs crossed under her. Her face was blocked by her hair as she brushed her doll's hair. The girl was ghostly white and partially see through.
Bellatrix took a step into the room and the girl's head snapped up to look at them. There were scars on the right side of her face, her right eye was missing leaving an empty socket and the left side of her face was torn off. She looked like she had been mauled by a wolf.
"GET OUT!" the girl shouted, her booming voice deafening.
"Bella, let's leave." Hermione backed away from the room, not wanting to run until she knew Bellatrix would go with her.
"That's a good idea." Hermione ran down the stairs and out the front door, closely followed by Bellatrix.
"That was horrifying!" Hermione looked pale and shaken.
"Yeah but thrilling." Bellatrix looked like she had had fun and wanted to do it again.
"You're awful!" Hermione punched Bellatrix on the arm causing her to laugh.
"I'm sorry 'Mione" Bellatrix apologised and wrapped her arms around Hermione. Hermione returned the hug briefly then pulled back and took her hand.
"Let's go home." They quickly made their way down the street to their house. They went inside, took off their coats and went into the living room.
Hermione put the TV on and went into the kitchen to make hot chocolate. " "Incendio" Bellatrix cast the fire-making spell into the fireplace and sat on the couch.
Hermione walked back in with two mugs in hand. She sat next to Bellatrix and handed her a mug. Hermione put on Netflix to watch Hunger Games: Mockingjay Part 1 then relaxed into Bellatrix's side.
Bellatrix wrapped her arm protectively around Hermione and they shared a loving kiss. Finally Hermione felt safe, warm and happy in her lover's embrace.