Kathryn Craft has written a superb roundup of ways to show your readers that a character is in love. Nine ways are offered up in this Writer Unboxed article.
How love changes the character.
How a character sacrifices to support their beloved being their best.
They can’t stop thinking of their beloved—even beyond death.
Lovers “see” each other in a way no one else does
Show mutual need fulfillment.
Deepening feelings lead to an emotional turning point
Show that love causes deep inner conflict.
Show the lovers sacrificing for each other.
Craft also has six things that don’t convince the reader of love. It’s worth a read, if only to see how love can change a story you’re creating. Plus how to show off some love.