Is it a figure of speech?

Yes, it is a metaphor, a comparison of something living to an inert object. In this case, her inner soul, her core, her true feelings are compared to some type of garbage for the neighbors to actively show their disrespect and judgment. Also, the heart, itself is an organ believed to be the core of love and true feeling. It is a very good book. I just read it again for the umpteenth time. Each sentence is written with such clarity.