I have a stalker on instagram?

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So on instagram, this girl has been harrassing me and others for months. She has made numerous fake account and pops up to us constantly, threatening to kill herself etc if we dont give her our addresses or instagram passwords. She uses fake identities and pictures and names so we have no idea who it truly is but she wont stop talking to me, even when I block her she finds a way to find me. she threatens us for phone numbers etc and I dont know how to get away from it, I feel really anxious and unsafe as this could be any old person and we dont know who Recently she hacked someones account too, and she has hacked many... What should i do?