Greeting the guests is part of being a good party host.
Although Winter may not be the one who organized the event, everyone's attention is more on her than on Bianca. Today, she's got the spotlight all to herself. Fortunately, she's no longer a stranger to how this kind of occasion plays out. After working so hard to meet the Middleton's standards back in her past life, she already memorized who these visitors are, the attitude she should use to approach each one of them, and even some hidden information about a number of them.
Officially, parties in high society are meant to be for networking. But in reality, those at the top use this to show off while those at the bottom try to appeal to them. It's exactly what she expects from rich ass people like them. Right now, she believes that she's at the middle at least.