In the state of Nevada can you get alimony from your husbands mistress

Short answer, no. Actually, alimony is only a payment from one former spouse to another.  What you appear to be asking about is the potential for "alienation of affections" or "criminal conversation" tort damages, both of which were specifically outlawed in Nevada several decades ago. See http://www.willicklawgroup.com/interspousal-torts/. The statutes are pretty strict, making it a crime to even threaten to bring such an action, so do be careful.  If in doubt, consult a family law specialist.