Drive to the house and give her a surprise knock on the door

when she opens, put the letter into her hand. Well, I think you must bring a friend (not relative) to actually hand her the letter. In my county, the service of letter must be from a non-related third party. A surprise visit can avoid her hiding away from you.

If she is one of those very bad tenants, you may have to hire a Mexican sitting outside the house for long time to deliver the letter.