One's ears are soft

耳根（子）軟 
[Pin Yin] Er3 Gen1 Zi3 Ruan3

If someone is very receptive to other's opinion, or don't know how to tell right from wrong while listening to others, we can say "his/her ears are soft".

"耳根" actually means the roots of ears, the small parts connecting one's ears and head.

[Example]
她的耳根子很軟，誰跟她求情，她都不忍拒絕。
She is so receptive that she will not reject whomever begging for her forgiveness.