He's not a tenant, please stop addressing him in such a manner. He is a guest of your tenant. My leases always had a provision requiring my prior written consent of any guest that stayed longer than 7 days.
I'm with Tevis - serve a cure or quit notice. When your tenant calls to try to cure, give her two choices - her guest either vacates the premises in the timeframe given or you'll file for her eviction. If she's in a talking mood, you might offer her cash for her keys in lieu of an eviction as long as she leaves the property in the same condition it was in when they moved in (you do have pre-move-in pictures, right? If not, serve a 24 hour notice to do something with the property and document the current condition before you serve).
It also doesn't hurt to let her know you just documented the property condition with pictures and that New York state allows garnishment of wages for judgements.
BTW - taking regular property inspection pictures before/after a lease starts/ends are great tools for documenting repairs, insurance issues, code compliance, use in court to illustrate damages. With just about everyone carrying a phone with a camera in their pocket these days, it's easy to document and save for later.
It only takes one problem tenant to change how you do business.