Adorable. She could handle some social awkwardness, even the shyness. In many ways, it was familiar, almost comforting. And she was encouraged by the fact the Doctor hadn't immediately fled when she had noticed the flirting.
But it wasn't until they were standing in front of Yaz's flat, her hand still in the Doctor's, that River let herself start to believe they might really be okay. They had survived 24 years on Darillium living linearly, practically sitting still. All of time and space to explore? Surely they could manage.
There was still that anxious part of her that always questioned whether each new version of the Doctor felt as deeply for her as she always still did for them, but it was getting quieter the more time she spent in her company.
"You're the weird friend," she said quietly, amused, "Why am I not surprised?"
River was less oblivious to the attention their closeness was getting than her wife seemed to be, and she gave her hand a gentle squeeze. "Dear, what did I say about introducing me properly?"
Yaz was still staring, watching the exchange between them with an intensely curious interest, but she looked ready to say something.