Is it permissible to share an audio clip of a girl reciting the Quran—without an image—on WhatsApp?

You are not permitted to share the recording that contains the girl's recitation of the Quran.

Familiarity between young men and women who are not mahram, even with the intention of marriage, is a gateway to temptation and a means to corruption. Therefore, you are not permitted to speak with or correspond with this girl without need. Do not be deceived by the fact that the conversation is about religious matters, as this could be a lure from Satan.

Laxity in these matters leads to dire consequences. Jurists have explicitly prohibited speaking with a non-mahram woman without need.

Fear Allah and close the door to temptation by severing this relationship. If you are desirous of marrying her and are capable of it, then hasten to marry her. Otherwise, turn away from her and occupy yourself with what benefits you.