One thing we could potentially do is simply replace “We’ll always be with you” and/or “But this is your fight” with some wording that could help clarify the intent of the original syntax.
“She was quick to learn in our training. But Leia feared giving in to hatred like our father, choosing instead to follow our mother’s path. Throughout her life, Leia lost everything. And everyone. But in the end, she still chose love. A thousand generations live in you now. Let her legacy guide you as you face the darkness.”
EDIT: A slight adjustment could nonetheless remedy the disconnect between the two ideas - “choosing instead to serve the galaxy with our mother’s compassion.”
If you understand that her mother’s path is to love and serve others despite everything, then the two sentences don’t have that “non-sequitur” quality. Padme fought for the Republic and Anakin despite losing both to the dark side. I know DZ said that Leia didn’t technically lose everybody, but I think that’s arguing semantics, especially because I hadn’t even considered how she lost her entire adopted family and home world. I was only considering what she lost in the sequels themselves. She lost her son to the dark side. She lost her brother first to the unknown for like 10 years, and then death. She lost her husband to that same son. She lost the New Republic she helped build. She lost nearly all of the Resistance she helped build. At some point you just have to accept the fact that Luke really isn’t exaggerating all that much when he says these things.
What Rey has to deal with in terms of loss is a cakewalk in comparison. Palpatine denied her a pair of loving parents. That’s about it. Thus why Luke telling her this story is meant to wake her up to the fact that she can overcome her hatred with love quite easily as a Jedi. All of this is wrapped up nicely in a conversation already in the film:
“All you want is for me to hate. But I won’t. Not even you.”
“Weak. Like your parents.”
“My parents were strong. They saved me from you.”
Her parents stood for the same type of love that Leia did. They all laid down their lives so that their children could live a better life.