What should i do about talking to this girl, because i don't want to seem like a pest?

There's this girl that ive been talking to and shes quite a mystery. the other day we had said we were going to see each other at a party but late last night as i was home and she was with her friends we were texting and i had fallen asleep without telling her. but later like at 430am she texts me saying shes not going to the party anymore. so should i now text her as casual convo saying like "sorry for falling asleep"? or should i ask her why is she not going? or should i just wait and see if she texts me?