Bit of a "sticky wicket." You should treat her as you would any other tenant, and have her served with a Notice to Quit, depending upon the circumstances, either a 14-day notice to quit for non-payment of rent, and/or a 30-day notice to quit, for which you do not need any reason, stating that last date is June 30th, either way.
The problem with a 14-day notice is (as with any tenant) if this is the first such notice in the past 12-month period, tenant can "cure" default by paying any and all monies owed, and eviction process stops, and you have to start all over again. I always advise my clients to send BOTH notices, and to have it served by the Deputy Sheriff (not very expensive) so you have an unbiased 3rd party who can attest to service of process.
This may be even more important in your situation since some unscrupulous persons (not saying she is, but...) might see this as an "opportunity" to claim "abuse" of some sort (perhaps pertaining to her child) which can take a VERY ugly turn of events for you personally, and result in you being locked out of your own home until she decides on her own to leave, whenever that might be, some time in the long distant future.
Best wishes to you.
No attorney-client relatonship is created in responding to this question, and advice provided is based solely on very limited facts presented, and therefore may not be correct. You are advised that it is always best to contact a competent and experienced with the practice of law in the county in which you reside, particularly as it relates to family law, child support, custody and visitation (a/k/a "parenting time") issues, including 209A abuse-prevention restraining orders (a/k/a "ROs" in legal-speak), regarding un-emancipated children, under the age of 22.
Serve her with a 30-day notice to quit citing her last day as June 30. Do this before May 31. If you are worried that she will not sign for certified mail, have a process server do it. You can use the Plymouth County Deputy Sheriffs' Office or a constable that you can likely find on line. Town Clerk's office can also likely tell you who the authorized constables in Plymouth are.
To questioners from West Virginia & New York: Although I am licensed to practice in your state, I practice on a day-to-day basis in Massachusetts. I answer questions in your state in areas of the law in which I practice, and in which I feel comfortable trying to offer you assistance based on my knowledge of specific statutes in your state and/or general principles applicable in all states. It is always best, however, to work with attorneys and court personnel in your own area to deal with specific problems and factual situations.