lets split

Lets split is another way of saying you wanted to leave with this person or depart from where you are. In this instance, the word split is talking about departing from wherever you happen to be at the time such as a shopping center, airport, or even your own home. It is most commonly used when you are at some sort of celebration, party or social event in which you will ask the person you came with (friend or date) to leave the party with you.