Do landlords need a reason to evict month-to-month tenants?

My girlfriend has a problem with her landlord saying that I (I have my own apartment) come over too often and that she doesn't like it and she's thinking about evicting. The landlord hasn't actually done anything yet, but she is worried that she might get evicted and she doesn't have anywhere else to go as she is a section 8 tenant in Michigan and there aren't many places that are decent and accept section 8 vouchers. There is nothing in the lease that restricts visitors from coming over at any time or for any amount of days per week and there hasn't been any written notice either. I don't spend the night either, so she can't say I’m living there. The lease is month-to-month though, and I'm trying to figure out if the landlord is just allowed to ask her to leave for any reason or does there have to be a violation for her to get evicted?