Tenant asking for rent reduction or threat of lawsuit

[Arif K.]

I have a tenant who has caused issues for me from the day she moved in. She has now sent me a letter threatening me with a lawsuit or I accept her "reasonable" offer of a 30% reduction in rent. I know this is bogus and I have sufficient documentation to prove so I am not extremely worried about that. The question I have is, am I in any way obligated to respond to this email she sent? In the past she has threatened me that her lawyer would call me the following week and I called her bluff. Can I simply ignore it or should I respond back in a terse manner and offer her again what I previously did, the ability to break out of her lease without any penalties.