tui1xin1zhi4fu4 【解释】：把赤诚的心交给人家。比喻真心待人。 treat a person with sincerity；be loyal in friendship；carry one's heart upon one's sleeve；confide in sb 1.我们推心置腹地谈了一个多小时。 We talked heart to heart for over an hour. 2.不要对他推心置腹，他喜欢乱讲话。 Don't confide in him, because he blabs. 3.那是我们之间第一次真正的推心置腹的谈话。 It was the first really intimate conversation we had had.

You can translate as your good friends.to your 推心置腹's friends,you can say everything you think.

even though she isn't really a mother but she's a trustworthy friend 推心置腹的 = trustworthy

[tuī xīn zhì fù] 把赤诚的心交给人家。比喻真心待人。the flow of soul