She always helps others with her open-hearted kindness.

open-hearted 是由形容词 open（开放的）和名词 heart（心）加上后缀 -ed 组成的复合形容词。open 表示"敞开的、不设防的"，heart 象征"内心、情感"。open-hearted 字面意思是"敞开心扉的"，引申为"真诚的、坦率的"。