To repeatedly force herself to say “it's fine” wasn't the hardest bit.
The hardest bit was to swallow the bitter truth that no one was ever gonna find out what she really felt when she said that. To hold back the things she really wanted to say. To convince herself that that wasn't at all pretence; that she wasn't lying to herself, nor to anyone. To finally realise she cared too much to bother about the warmth that was streaming down her face. To accept the fact that the person she thought was the only one to really know her, might not know her at all.
The last part was the hardest.
Silence was too loud for her to hear her own thoughts. So she closed her eyes, wishing for anyone to never have to feel what she felt. And just like that, the horrible night passed.