What is Martha’s response when Jimmy tells her that he still loves her? How is her response explained?

Martha is unresponsive to Cross' confession that he's always loved her.

She had never married, she said, and probably never would. She didn't know why. But as she said this, her eyes seemed to slide sideways, and it occurred to him that there were things about her he would never know. Her eyes were gray and neutral. Later, when he took her hand, there was no pressure in return, and later still, when he told her he still loved her, she kept walking and didn't answer and then after several minutes looked at her wristwatch and said it was getting late.