No a formal would be more like the icing on the cake, you see. As with Benson and this Lyss, they are already getting to know eachother, taking her as date to a formal would be like a subtle invitation to a higher level, and she would most definately get that. Understand?
I know you do.
Reversedly asking someone to a formal could serve as a base on which to start to get to know a girl you like, if you haven't already prior to the event. And for that purpose it's also good. It's a nice, special event for such a gesture.
Chicks in particular dig this shit, you should not underestimate that.