Should I go after her?

Well you should talk to her and tell her that you are sorry for the way you were acting and that you didn't mean to hurt her feelings.

Try to talk to her and see what would happen or just call her and explain to her on what happened or tell her why you have not called her.

Explain to her that you have been a bit stressed/pissed for the last week. And let her know that you didn't mean to brush her off. If she reacts with lack of understanding/empathy then maybe consider not going with this girl. Remember, if you are the type of guy that likes to be alone when you are stressed/pissed etc. & can't seem to understand that part of your personality, it maybe better not to continue with this girl. Some girls (and guys too) need to be with their partner, need to communicate with them through stresses/achievements/ etc. Other people need to have their space to work their emotions (ie. Work-out, play vid games, etc) they just need to re-charge themselves. Judge whether this girl is gonna turn 'cold' when you need your space or whether she will support/understand this aspect of your personality. Maybe you don't need to be alone on your own when you are going through stresses. Perhaps you can welcome this girl as someone you can confide in (if that is your style). Anyways, let us know how it works out!

When you see her, explain that you were a little stressed that day and apologize to her... send her an sms in your free time that you're thinking about her or something like that...