Well, personally, I'd say, "According to my policy, blah, blah, blah...., and I can't show favoritism and have to be fair to the other students. I've let this go twice already which is more than agreed to, but I have to warn you that if this happens one more time, I need to drop your daughter. It's not fair to her, me, or the other students."
I've put my foot down on this and on payment issues twice this year, and the parents realized I was serious, and it's been alot better since. You're giving grace (one more try) but at the same time being stern (that's the last try).
In the end it's up to your descretion. The problem with my suggestion is that, if they do it once more you have to drop them, or else you'll never be taken seriously again. You could say, one more time and then she gets a suspension, meaning she can eventually come back. There's pros and cons to every aspect. The con being her learning is interrupted, the pro being you don't lose her. These are just some thoughts. You could really put the parent on the spot, and be like, we have a problem. This is what it is. What do YOU think we should do about it/ to correct it/ to avoid it happening again? (staying polite, of course).