There are intervals of silence in the interaction between the landlady and the prospective tenant. What are the reasons for this?

While conversation between landlady and tenant, when tenant said landlady that I warned, I hate a wasted journey and I am an African, with this a silence came into existence with a voice of breathing in it. Landlady started inquiring about how dark that tenant is as he was African. The main reason behind it was landlady felt inferior listening this and she had given a small pause before replying to an African. The sudden pause shows that when lady got to know about African’s race she was bit disappointed and suddenly put a question on his skin colour.