Wait o, is it mandatory to greet her or to go and greet her? I am confused, I mean, it is okay to respect our elders and greet them when we see them but to go and greet her like if she is not outside, I should go and check on her through the window to greet?

As for the other landlady that do not want a yahoo guy, I don't think her problem is really yahoo but the behaviour of yahoo guys, they keep many friends, one rents a house but like 5 start living there with him, and most time disturb the peace of the house with their weed... No landlord/lady would want such so I think she was just being extra careful. infact most landlords ask such questions nowadays to know the kind of person who want to rent their house.