My question involves landlord-tenant law in the State of: Massachusetts

A co-tenant and I signed an at-will month-to-month rental agreement. The agreement provides that either the landlord or an individual tenant can leave at anytime, if they provide 1 month's notice, e.g. notice before end of August, leave at end of September.

My co-tenant has made several violations of the lease agreement:

1. She brought in 1 extra resident (her partner) without informing the landlord. The lease allows for only 2 permanent residents.
2. She brought in an additional resident for a period of over a month. The resident has left, but he stayed past the limit specified on the lease.
3. She and her partner smoke cannabis daily in the apartment. They do not have a permit for medical cannabis or for recreational usage.

Additionally, my co-tenant has asked for me to pay 50% more of my usual share of the rent. We didn't have a written down roommate agreement, and obviously the landlord doesn't give a damn how the rent gets paid, only that he gets all of it each month.

My co-tenant has no/poor credit (history) and also negligible income (on the order of maybe $150/week). Her partner helps supplement the income, but he is not on the lease.

On the other hand, I have excellent credit and a lot more income--enough to rent the apartment out by myself.

Given all this, is there anyway I can discuss with the landlord about giving notice to my co-tenant? What risks are there in doing so?

Please advise.