Spoiler — from the ending. Tap to reveal.
“So what if he already has a girlfriend? I think it's worth giving it a shot.”
2 quotes from Sailor Moon, each with commentary on what it means and why it stuck.
“So what if he already has a girlfriend? I think it's worth giving it a shot.”
“Usagi is someone we love with all our hearts. Nehelenia, haven't you ever had a true friend like that before?”
The easy reading makes this a taunt: the strong one, cornered, throwing friendship in a villain's face. It works better as a diagnosis, and the next episode treats it as one. Nehelenia's immediate reply is contempt (a friend is useless, and Jupiter can be sealed away with the rest), but in [5.06] she gives the answer Makoto's question asked for. Before the mirror, she tells Usagi, she was worshiped and all alone, with no one to share her joy or her sadness, and she made herself the only friend she needed. The battle ends when Usagi offers her the very thing Makoto named, promising that everyone would be her friend, and the Guardians follow with lines like Uranus's "You're not alone anymore." Makoto, weakened and still calling for Usagi to wake up, asks the one question in the arc that gets an honest answer. It is less a boast about her own friendships than the first accurate read of the enemy, made from inside a trap.
Here is the case against the line. In a montage meant to show what each friend means to Usagi, Makoto is remembered for chasing a boy who is taken, which shrinks her to the running joke of an episode titled "Jupiter, the Powerful Girl in Love". The page makes that case stronger. The DiC dub's flashback line for her in the same montage is also about boys ("Still too many guys we gotta meet"), so two separate English scripts agreed on the one thing to remember her by. Concede that much: it is a narrow memory. The answer is what the memory is for at this point. Princess Serenity is about to ask four dead friends for all their strength, and the stage directions have their ghostly figures appear and give it. Of the four Viz flashbacks, Rei's is a denial, Minako's accepts a loss and Ami's describes a feeling. Makoto's is the only one that urges an attempt at bad odds. It is the right memory for that moment, and Usagi acts on it.