Dear New York City Tenant:
A roommate is not required to provide advance notice to the landlord (prime tenant) when intending to move out, unless there advance notice is required by a written agreement. In any case, if your text message were considered the same as a written notice it is insufficient. A one month notice ends the arrangement on the last day prior to the next rent due date.
In my opinion, your prime tenant is a lawbreaker. The roommate law allows only one roommate, not two, and the person in the "room" is a roommate and not a subtenant. Your prime tenant exceeded by one person the maximum allowed roommates if she is the only tenant named on the lease with the landlord.
So she cannot hold you up. if she sues you (highly unlikely she wants her illegal profiteering scheme exposed to her landlord) you have defenses. But since she cannot claim any legitimate entitlement to damages, her threat of lawsuit is hot air.
The answer provided to you is in the nature of general information. The general proposition being that you should try to avoid a bad outcome if you can.