Eevee:
maybe Maiden Holmes - chinese historical drama. FL is serious and tough, she does her job well. I haven't watched this yet but I'm pretty sure she becomes more open and gentle after meeting and falling in love with the ML.
sarrymast:
Angel's Last Mission: Love comes to mind.
michelleoc:
Not actually a romance, but I can recommend XX for two strong female leads. It's only five episodes and the cinematography is great!
jeseania:
I didn't watch it, but I heard the FL is like that in The Wonder Woman. I think it fits all your requirements ;)
maehawk:
A japanese drama here : https://mydramalist.com/12468-date-koi-to-wa-donna-mono-kashira
The female lead is really serious and cold, but deep down she's a real romantic, I really love the female lead here, she is strong, smart and knows what she wants, the male can get a bit annoying but they made a cute / weird couple
Personally I really enjoyed this drama, even though the rating is not very good, it has a lot of charm
Thanks for recommendations! I'll look at them.