If a woman who is an aquaintance and tells you her nipples are hard, what is she trying to tell me?

This woman in her mid to late 30's is an African American woman who I bowl with on a near weekly basis and I am a white guy in my mid 40's. I rub her arms, shoulders and neck usually when we talk. The past few times I have done so she has told me that her nipples are hard from what I have done. I believe she knows that I want to be with her, but I do not want to jump to conclusions here. Any ideas here from reliable sources please!