It was odd for Ella, whose specialty was the control of her own mind and the minds of others, to have someone inside of hers, even if it was Terrence. Her raw instinct was to abort the connection as soon as she realized most of the things she had cluttered in the forefront of her mind were open to him, but she remained steadfast. In the long run, it didn't quite matter that some of those thoughts were how she truly saw him or how she felt about her brother leaving for school the next day or the worry she encountered over how this day would continue. Perhaps it was better for him to see her thoughts like this, see the things she'd never been good at verbalizing, before he knew the truth.
Subconsciously, she could feel herself twisting the sheets in her nimble fingers as she tried to let his mind search deeper into hers, bypassing things she didn't want others to see, like the memory of seeing her childhood home while she was in Bulgaria but not being able to go in, or the memories associated with the days of Durmstrang or the first time she'd met Terrence. Most of these were all things stuck inside of her head that were buried easily and not so easily resurfaced, but they had to get through them before they could get to the end point where the secret lay.
She kept her eyes unblinkingly on his, her expression unreadable. It didn't matter what he saw on the way there, all that mattered was what he found when he got there. After another layer of even more deeply buried thoughts and memories, things she hadn't thought about in years, nor had any desire to think about again, they reached it. Like a chest opening to reveal a buried treasure, the memory of the day she was Marked appeared. It was almost like a Pensieve, how vivid it was. She could feel the Mark burning where it had been branded into her skin, moving and slithering as though she wore a true snake upon her arm. Glowing lines from the vow she'd taken to never speak of secret she was being given criss-crossed imperfectly around her arm. Looking up at the snake-faced man, it was the voice beside her that spoke, the voice of the Minister of Magic, explaining that secret she was now to keep. The Complacens potion.