I wonder if Xiu asked Song to bid on the painting. Youyan notes that he's been looking and smiling at her, and since Xiu doesn't seem surprised that Youyan was the one who asked Tao to buy it, it's possible this was all a test (or a tease) from Xiu to Youyan to see how she'd react. And they both used someone else to actually bid as a cover.
That would not explain the glare she sent him. It was pretty spicy
Oh dang, I totally missed that! Yeah, I agree with folks now, it seems like Xiu was definitely not appreciative of his attempt.
It's interesting to think about the differences between this life and the original one. Youyan doesn't seem to know much about Song and Xiu's relationship beyond that it happened, and that she immediately abandoned their wedding and marriage to mourn Youyan. But I think how they got together the first time is going to be relevant, especially as Youyan's changes ripple forward.
She and Xiu already have a much better relationship than last time, so it seems unlikely Xiu is going to be actively moving toward Song, but clearly something pushed them together the first time around. Family pressure? Comphet? Some kind of publicity thing? Or maybe Song just really likes Xiu and, originally, with her heart broken she didn't see any reason not to accept?