i am pissed off with this girl again

she wanted to buy something from me, took the stuff and owed me the money for more than a week.
I reminded her again this morning and she just said "oh, i forgot about it", walked away and that's it.. no action also.
Now after lunch, i had to remind her again, and she told me irritably that she pay me the money today (i wonder when).
Arrrrrrrrrrghhhhhhhhhhhhhhhhh!!!!!!
