More books labeled as 'Urban Fantasy' popped to mind.
Michelle Sagara's Chronicle's of Elantra starting with
Cast in Shadow. They make a point of the heroine's youth so she might be under 20, but the romance is still iffy after 5 books. The world is original, not Earth+.
Eileen Wilks' World of the Lupi starting with
Tempting Danger. The heroine is closer to her 40s than 20s and the iffiness of the romance is not that iffy. This is very much an alternate Earth setting and Urban Fantasy vs. fantasy that is urban so might not suit.