Draco is her second cousin. And if he tries, I have pointy shoes at ready. This Post included a flash back, which is separated by a line of dots.

Suddenly the wardrobe rattled. 'Good god, not more boggarts.' said Sarah. 'How do you know?' asked Draco. Sarah tapped her magic eye. 'Ahh Ok. I know how you struggle. I'll do it.' said Draco. 'How do you...' began Sarah and then she stopped as she remembered one of Lupin classes.
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Pavarti had just turned a snake into a jack-in-the-box. 'Very Good Very Good! Sarah next!' said Lupin. Sarah had stepped up, then watched in horror as they turned into the 4 people who she dreamt about, had nightmares about. They said their words, they did their actions. 'R-R Riddikulus!' she said in a shaky voice. But it all became too much. She collapsed. Lupin ran forward. The boggart changed into the moon, which changed to a ballon. 'Neville, finish him off!' said Lupin. Neville strode forward, and they all caught one last glimpse of Snape in his green dress, before Neville laughed and it exploded. Lupin and Harry ran forward to Sarah. 'Why do you think Sarah's boggart has Lupin in it, nodding to Sirius Black saying we don't love you?' whispered someone. 'It's obvious. Sarah was raised in an Orphanage, until she was 13. Sarah Black, Sirius Black, he's her Dad, Lupin is her god-father. If neither of them love her, or want her, she has to go back to the Orphanage. You haven't noticed the cuts and scars and bruises all over her body? That's who the boy was, and the woman.' whispered Hermione crossly. Meanwhile, back at the front... 'Sarah. Sarah! Wake up.' said Lupin shaking her. Sarah opened her eyes slowly. 'What the...' she said, before she became concise of everyone staring at her and realised what had happened. She turned bright red, grabbed her back and ran out the room. Lupin heard a sob. 'Right ok, 10 points to everyone who tackled the boggart and 10 to everyone who answered my questions. Class dismissed, off you go' said Lupin. He walked out, knowing he had no class next and went to find Sarah. He knew she had Divination now, but he also knew she had given that up. 'Forget that teacher. I only ever learnt two things in her lessons. She's a fraud and Divination is a waste of an hour.' said Sarah when she had told them. He had a suspicion where she would be. Sure enough, when he went through the room of Requirement doors, which he knew how to get into, he found Sarah, curled up on a large beanbag. He looked round and saw she had done a pretty good job imagining this place. There was comfy bean bags, luminous star lights, and the walls were painted by just getting a brush, a colour and running along with the brush on the wall. She had stuck things on it though, things she felt mattered. He sat next to her. 'Sarah.' he said. 'Everyone else can do a boggart. Why can't I?' she said. Lupin sighed. 'Because you have had a more troubled childhood then any of them. You need time to regain your strength.' said Lupin. 'Not fair.' said Sarah, but Lupin heard the note of silliness in her voice 'Not, life isn't fair.' he said.
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Sarah watched Draco. The bogart came out as his father. He raised his stick. 'Riddikulus!' Draco said, pointing his wand. His father automatically started to do a tap dance. He gave a laugh and it exploded. 'You're scared of your Dad?' asked Sarah. 'Just when he is angry.' said Draco, lowering his wand. Draco turned to face Sarah with a grin on his face. 'You look so nice when you smile. Ever thought of doing it more often?' asked Sarah. 'Why you!' said Draco, and he jumped on Sarah. They started to play fight. Sirius later found them on the bed, giggling and poking each other. 'What are you two doing?' he asked. 'The Deadly Finger duel with commentary.' said Sarah. 'And Sarah get in with another spectacular poke!' Sarah said poking Draco. 'And Draco comes back with a incredible poke! What a poke, what a guy!' Draco added as he poked Sarah. Sirius grinned and shook his head. 'How did you two come to be like this?' he asked. 'Well. You and Mum loved each other very much...' started Sarah. 'Thank you.' interrupted Sirius. 'I taught her how to play-fight, she taught me how to laugh.' said Draco. He stood up. 'Let's see if you pay more attention to name then you do to Snape.' he said, and he leaped on Sarah. 'No you don't!' Sarah said, and they had a fight. 'What the bloody hell!' yelled a voice. Draco was blasted off her. 'What the hell are you doing Malfoy! You low-life slime!' said Harry. 'Do you mind? He's my cousin.' said Sarah mildly. 'And it was only play-fighting.' she added, ducking under Harry's arm and pulling Draco up.