Either in the past, or as Hydaelyn taking aside the WoL for a private word in the present. Being Hydaelyn is/will be a stressful task, and the WoL will quite willingly eat her out as a treat and/or a show of trust.

Bonus points for:

The WoL is used to being a top, but lets Venat ride their face as she wants.

There’s a bond of surprising trust between them, despite not truly knowing each other for that long.