Tenant Wont Pay rent and Wont sign Lease

[Ana Gupta]

We purchased a property 4 months ago and have not been able to get the current Tenant to sign the lease. She has been paying the rent amount for the past few months that she originally paid to the previous owner. Every month she threatens not to pay the rent and to this day has not paid on time. This month she still has not paid the rent and we are on the 8th of the month. We went over there and told her to sign the lease and she refuses because it is for the amount that she does not want to pay.  She wants us to give her a discount but this is the amount we are charging other tenants in the same condo. She texted me last week saying she was leaving on the 19th of the month.  I told her I would pro-rate the rent and she responds a week and a half days later that she is no longer leaving at that point the rent was already 2 days late. 

What are our options here? We don't have a current written lease with her, she is not paying the rent on time, when she finally pays she isn't paying for the full amount we have requested.