Colorado Month to Month termination

[Chris Hertig]

We  inherited tenant who is a nightmare!  She has been there for many years, her lease expired three years ago, and up until recently she has been tolerable.  A couple of months ago, we presented her with a new lease, which included a rent increase, and she has become combative and has refused to sign.   She needs to go, but I want to be sure I give her the correct amount of notice.   Because she is month to month, am I good with just the 21 days?  Or do I have to follow the timeline of "A tenancy for one year or longer, ninety-one days;..."  ?

Thanks!