It really started after Sirius died.
The surviving Weasleys had been ordered into hiding, separately of course. Ginny, aged seventeen, had been sent to stay with Remus and Sirius, miles from anywhere. She helped around the house, and locked the cage when Sirius couldn't be there.
When Sirius didn't come home, and word came that he'd been captured, she found herself needed in a different way.
The morning after that full moon, she found Remus huddled and sobbing in the corner of the room.
Knowing comfort was needed, she healed his cuts, then tackled the other wounds with a kiss.