[She doesn't want to be reasoned with or handled or pushed right now. She doesn't want to agree it was great sex. She doesn't want to make the best of it. She needs time to process and right now there are just a lot of words coming at her from two people she cares about a lot.
The mature thing to do would be to take a breath, relax, apologize.
She won't be doing that. At least not right now. She's hurt and offended that Reid would relate this to their first time. She wanted him and he wanted her. They'd just been holding themselves back that time, right? So, did that mean he'd never wanted her or that he'd always wanted Rebecca? Either way, she wasn't feeling good about it.
The thing is she's not good at being hurt and offended, much less in a "crowd," so while the expression flashes on her face it's replaced by more anger which is an emotion she's comfortable with, and right now she has to hold on to anything comfortable.]
I'd hate to be pissy and full of ruining everything. I'll get out of your way and you two can bond over all the great sex. [And, yes, turning to go. Another thing having a power like phasing can do for you is making escape feel like a really solid option.]