In this case, drop it. You only make matters worse for yourself if you pursue it. Keep this in mind when you plan the activities. You may even do something during the day rather than in the evening. Save formal dates for later on when you are more comfortable with her.
Most men do the opposite.
Formal dates at first, and then as the relationship develops, the dates become more and more casual. This can imply to the girl that she is being taken for granted. It's very informal. Come and join us. You'd have enjoyed it.