How to deal with a mean person?

[Canadian Beast]

I have my 21st birthday coming up next week. I invited an underage friend of mine (she would be let in if she brought her parent). She said she was going etc.

Then because of some silly Facebook thing (I reported her posts to be funny because that's what we all do to each other - in a playful way), facebook banned her for 12 hours from using it. I didn't mean for this to happen..but you know...it just did. I was about to apologize to her but then...

She then proceeded to block me, and tell all my friends not to go to my party and not to tell me so I would still have to pay for each of them ($30 per head).

Our family are really struggling to pay for this party at the moment (to the point where I may have to sell my car) and this kind of nonesense over something as stuipd as facebook...just doesn't seem right. I feel offended because I spent 2 hours filling out a minor attendance form for her to get in, and paid for both her and her mum...

I admit it was a silly prank but I really think telling people to betray my party (as the expense of a poor family trying to pay for their sons birthday is overacting).

How do I go about handling this?

Thanks guys