Complex sentence: It's Valentine's Day and after comparing cards, Will catches up with Charlotte, to whom he sent a card and a bouquet of flowers, and she invites him along to an underage disco in which she will be bartending.
Split into simpler sentences: It's Valentine's Day and after comparing cards, Will catches up with Charlotte, to whom he sent a card and a bouquet of flowers. She invites him along to an under-age disco in which she will be bartending.