Well, everyone knows that these things happen, but it is yucky when it's right at the start of the school year :-)
I think it would be nice to give her something for her time. You can look at it this way.... The teachers here at CPS are paid (on average) $40/hour for 'after school' duties - which means if they are a coach, drama sponsor, tutortime, dance etc. So, if you were 30 minutes late that is basically $20 she "should" have been paid. Clearly you aren't going to hand her $20, but what about supplies? You could tell her that you would love to get her some additional supplies for the class - is there anything she didn't get enough of that the class still needs?
The other thing you could do is trade time for time, so "give" her 30 minutes of your time..... could you bring home papers and grade them for her? help her with her overhead slides? Type up a newsletter for her parents?