Adding Tenant to Existing Lease

[Keaton M.]

This is a twofold question.

1) I have a long term tenant who has been great. He pays early, quiet, respectful, and not needy. He had a friend move in with him for the summer. Is it reasonable/possible to put her on a month-month lease and keep the existing tenant on the 1 year lease? I don't want to give her a term lease, but how would I keep the leases separate? 

2) The tenant moving in had to break her previous lease due to abuse relationship. She paid all the fees to the previous place, but did break the contract. She also has a felony 2 years ago that is being moved to a misdemeanor soon. Would you allow this person to inhabit your rental? These would be warning signs for tenant screening, but since the existing tenant was paying rent on his own and she would be month-month with a security deposit, I see this as less risky. I just don't want to open the doors for a terrible situation for everyone. 

Thanks