Did the irrepressible Luna Lovegood have a thing for Harry Potter’s best mate, Ron Weasley?
Perhaps, though more likely, she was simply reacting to the effervescent presence of an accepting group of peers.
…Ron… …lowered his voice to (Gregory) Goyle's low grunt… “I... must... not... look... like... a... baboon's... backside.” Everyone laughed, but nobody laughed harder than Luna Lovegood. She let out a scream of mirth that caused Hedwig to wake up… …and Crookshanks to leap up into the luggage rack, hissing. Luna laughed so hard her magazine slipped out of her grasp, slid down her legs and on to the floor. “That was funny!” Harry Potter and the Order of the Phoenix – J.K. Rowling
We should remember that up to this point, Luna was probably not used to people including her in a friendly conversation or even just providing her any positive attention, since the death of her mother, Pandora Lovegood.
Think about that.
Have you or anyone you know, perhaps someone you went to school with, ever have a close family member pass away?
It is sad and it is traumatic; it is also often difficult to get close to that person, either to make a personal connection or even to physically be near them.
We feel awkward; we want to tell them it will be okay, that we understand, but the truth is, often we do not yet have the experience of such devastation and feel we have no right to speak on the subject.
As children, not knowing how to politely or properly respond, we sometimes reject the suffering kid because we are naturally fearful of the reminder that we will eventually have to deal with the same ordeal at some point in our life.
A reflexive response is to push away from the sufferer.
Luna had clearly experienced a great deal of this rejection after Pandora’s death.
The inclusion into Harry Potter’s circle of influence was likely both a release from the shackles of despondence and a shot of adrenaline that comes with the reintroduction to friendship.
It’s no wonder Ms. Lovegood laughed so hard; it was likely the first time she had done so in a very long time.
Ginny Weasley had extended friendship to Luna, but one person, alone is only a life-preserver; certainly significant and valuable, but a group of friends is a lifeboat and one that usually finds dry land where one can get their feet back underneath them.
Luna would become a vested member of Dumbledore’s Army and an indispensable confidant to Harry Potter himself.
"You could've taken anyone!" said Ron in disbelief over dinner. "Anyone! And you chose Loony Lovegood?" "Don't call her that, Ron!" snapped Ginny… Harry Potter and the Half-Blood Prince – Rowling
The Boy Who Lived would, of course, take Ms. Lovegood as his date to the Slug Club Party hosted by the loquacious Professor Horace Slughorn.
An immediate and superficial response to Harry’s invitation would be to assume a romantic crush by Luna on Harry.
The heart of the matter is that Luna was just happy to be seen as both a young lady and a friend by young Master Potter.
While we never see this particular event, Luna was emotionally crushed by witnessing her mother’s death.
A resilient child, she would rebuild her world with emotional fortitude and psychological strength to match the Chosen One.
Luna could see the world more clearly than any of her peers; she recognized immediately that Harry’s invite was platonic.
For someone so previously shunned by her peers, she would accept as much as Harry would provide, with no demands, nor even the inkling of a wish for more.
Such is the only requirement of the lonely outcast.
Her (Luna’s) prominent eyes swam with tears… …staring at Ron. …he looked around at the others, who were now laughing… …at the ludicrously prolonged laughter of Luna Lovegood, who was rocking backwards and forwards, clutching her sides. Harry Potter and the Order of the Phoenix – Rowling
Did Luna Lovegood have a crush on Ron Weasely?
Probably not; there were more important things in life for Luna.
Namely, returning from the depths of emotional anguish from which she was dragged by her mother’s death.
On that trip on the Hogwart’s Express when Luna responded to Ron’s ridiculous joke, the emotional release of laughter was simply a rush of happiness filling the void in Luna’s soul which had been so vacant for so long.