threats via email from brother in law and sister in law

My huband's sister in law created immense problem during my marriage.she imposed verbal insults and abuses to me and my family.gifted us damaged and fake gift items.when confronted she had sent this email.what step can i take against her?this is the email she had sent. oh dear dear .... what a performance .... I could almost visualize the applause of the rural crowd watching this "jatra". I thoroughly enjoyed the remarks posted, it provided with a great entertainment on an otherwise dull Sunday! But it exposed the hollowness of your education and sheer lack of any semblance of family values. I was bemused by your claim of the fake jewellery being gifted. It does not astonish me anymore. It is far beyond your intellectual capacity to gauge the price as well as emotional value associated with it. And you simply do not deserve such a precious gift item, hence I instruct you to return the piece along with the box and all accessories. Kindly arrange to have it sent back along with any other pieces of so called "fake" gift items to my in-law's place immediately. This episode also makes it very clear about the motives behind the fake story about the damaged sarees. It was a blatant lie and done deliberately to malign us. I hope that was the last time I heard from you. Please stay away from my family and my in-laws and their extended family and refrain from posting to me ever again. We could do without the existence of your and your mother's wretched selves from our life. And one more thing, cyber bullying and posting obnoxious messages is serious offence. I will take care to preserve this piece of evidence for future reference and share it with some of your relatives if required. I am sure you do not want to miss out on your american dreams or see it shattered so quickly.