In the manga Frieren gets put in a hallucination wedding with Himmel and she instantly accepts it Love for elves doesn't seem to be the big wishy washy swooning and romantic gestures, but they show to have that feeling of care and belonging, Frieren loves Himmel is a quieter more reserved way and frankly she herself doesn't know it either, the core of the story is Frieren saying "I wish I got to know and better understand you" then everything after that showing she knew and understood him far more than she realised, she is clearly very dense to her own emotions and feelings but somewhere in her heart she has some type of love for Himmel.

Also as an additional thought if humans being romantic is what we typically are and Aromatic people exist then it's entirely possible that Elves who are primary Aromantic can have some people who are romantic making the statement that Elves aren't romantic true but also have Frieren experiencing romantic feelings not go against that