don't be too sorry with her, If you explained why you had to go you don't need to tell her again. If you left suddenly then its ok just send her an email like "lastnight I went to XXXXX, would of loved to stay and atleast chat with you for a bit but I was literally out the door. Message me again and Im sure we can try it again lol,

"
one thing I try stay away from is Apologizing too much online. Just isn't MY style because it tends to send a needy "im trying win you" type of vibe in my opinion.
If you did explain to her why you had leave lastnight, just comment her picture briefly so she gets a notifier of new comment and you can be on her mind again, and shows you wern't blowing her away.
Theres lots of ways you can go with this lol.