How to reject an applicant for rent?

[Justin Wilcox]

I have a room for rent and I happen to know that the person who wants to rent it would not be a good tenant because they have had not paid their rent in the past and cause problems for other tenants. 

It was not documented as far as I can tell, how else do I go about rejecting this application?

The source telling me this is a close friend who lived with her at one point. 

Legally I want to stay out of trouble. 

I asked for a list previous landlords, and she did not provide the previous landlord that she had issues.

Thanks BP!