Please note that this scene takes place in Ginny and Luna's second year, when Ginny is being possessed by Tom Riddle… I like to imagine Luna trying to help and look after her from behind the scenes. I imagine them getting together in 6th year, so Luna has a long time to have a crush on Ginny before asking her out!
They had been in herbology when Luna had first realised just how beautiful Ginny Weasley was. They had been potting mandrakes together: the redhead's soft hands against her own, patting down earth. The freckles that dotted her skin, the curve of her lips, the way she moved, so gracefully.
The class had begun normally enough. Professor Sprout had thrust two pairs of bright pink headphones into Luna's hands, one for her and Ginny, who was staring uncertainly at the rows of mandrakes. She looked apprehensive, but when she saw Luna coming toward her, she offered a weak smile. Ginny hadn't been looking well recently, but this could be just because of the general stress the whole school had been under. What with students regularly being petrified and, in a dramatic and ironic twist The Boy Who Lived becoming a prime suspect, everyone had been rather jumpy lately. Luna smiled reassuringly at her and offered a set of neon headphones, hoping to cheer the girl up. The headphones clashed horribly with Ginny's hair, but Luna rather liked it: it gave a radiant, cheerful effect, brightening what was a horrible morning- grey sheets of rain slamming against the glass panes of the greenhouse, a shivering chill in the air. As they began to prepare their mandrake for potting, Luna glanced at Ginny, carefully assessing her. No, it wasn't her imagination: she was definitely thinner, she had dark hollows under her eyes and looked exhausted.
This wasn't normal. Everyone was a little more stressed out, but Luna hadn't seen the situation impact anyone to this extent. And Ginny was normally so robust: quick to argue, boisterous, fiery. This quiet, listless girl worried Luna a lot.
Luna watched as Ginny raised the screaming mandrake out of the soil and helped her quickly repot it, pressing down the earth around it as carefully as she could. Somehow, she didn't think Ginny would appreciate attempts to get involved directly. An innocuous remark such as 'are you alright?' could cause the girl to take tail and run, and then Luna wouldn't be able to talk to her at all. Luna, walking to stand in line for more compost, chewed her lip contemplatively. Lost in thought, something suddenly caught her eye: Ginny was staring at her. As soon as she realised Luna had noticed, she looked away. But in that moment, Luna felt her heart race- why was Ginny looking at her? What did Ginny think when she saw Luna? That she was pretty? She stared at her hands, spooning compost into a tub.
Ginny Weasley was very pretty. It was a fact, everyone knew it. Ginny Weasley had been looking at her. Secretly. When she didn't think Luna noticed. Surely this meant something. Luna sneaked a glance at the girl, who was now innocently shaking soil off of her trowel, her pink fluffy headphones bobbing with the effort. Luna felt her cheeks flame: whatever this feeling- this crush- was, it needed to be tamped down for now. Ginny didn't need an admirer at the minute, she needed a friend, and Luna would try to support her as much as she could.