Not renewing a tenant's lease

[Ivan Paxton]

I own a four-plex and live in one of the apartments.

One tenant's lease is up for renewal in early January.  She is a single Mom who has had an undesirable "boyfriend" hanging around for several months.  I'm not sure if he stays the night often, which would be a breach of the lease, but he does seem to babysit a lot.  There was a case of minor damage recently, caused by carelessness but the apartment seems to be in reasonably good shape.

The tenant has been late with her rent two times in the last year.  Both times she paid rent and late fees after a few days.  Today I had a call from a charity she has approached for help with her rent.

I have decided not to offer her a new lease.  I want to write to tell her but plan to wait until I have this month's rent.  Does anyone have a good form of words for my letter?

Thanks in advance.