Sure, there's a fair share of sassy, independent (usually poor) women in KDramaland - often confronted with the typical male lead, who is super rich, but morally and emotionally flawed. The sassy woman saves the flawed man through love - and the previously-flawed man saves the previously-poor woman from misery through wealth (and love).
This formula works oh-so-well and I never grow tired of it - but Eun-soo and Arang are particularly great, because they are different.
That said, I am curious to see how (if?) the budding romance in both shows is going to change them - and whether the writers will be able to keep them as strong and independent once the romance(s) get going (if they get going). Because one of the big issues I have with in-love female leads is that they usually become mere shadows of themselves when united with their OTP.
In this department, the shows are on different tracks. There is no heartache in Faith (yet) - the two leads are getting steadily closer, it's a sweet babystep kinda romance that is nudged along by Eun-soo. The drawing closer is great to watch (and Lee Min-ho's acting is at its best in these scenes), and it seems much too early to bring up obstacles ... though I bet one of them will soon realize that time-travel and romance have a tendency to not go together well. It is a fairly conventional road to love, though probably slower than some, and that's why I do fear for Eun-soo's independence. The worst that could happen to this character and the entire show would be a change in the power-balance between the Doctor and Choi Young. I do have faith (chuckle) in the acting abilities of Kim Hee-Seon, who is doing an excellent job so far, but I do not entirely trust the writers of this show. Please, writers, don't make her go all soft and gooey! I'd mourn the death of a great character, I truly would.
Arang is an entirely different case. Goodness, there is heartache in Arang (Lee Jun-ki's pained eyes last week! I cannot forget them)! While the (soon?-)couples in both shows have an issue of limited time/borrowed time, Arang's writers have been super cruel to make this the center of the romance-trope and have nothing better to do than constantly remind us of the hopelessness of this love *sob* The male lead has accepted that their time together can only be short, but he doesn't care ... or he might have hope that it’s somehow not true, that they can somehow make it work beyond the one month they have left. He is human after all and has always been (though on borrowed time) and human beings have that sad tendency for hope – and also for denial, because of hope (come to mama, Lee Jun-ki, I will hug you!!!).
Arang, on the other hand, has no memories of her previous life and she has a limited time on earth. She has no past and no future. While she cares deeply for Eun-Oh at this stage, she is keenly aware that if he admits his love (to himself, firstly, and to her, secondly), he will suffer great, great pain. It is his pain that she cares about, not hers - and that is why I think she will try to keep her distance from him.
Both noble idiocy and terminal illness (or, god forbid, amnesia) are classic obstacles in KDrama and I hate them both or any combination of the two with a vengeance. In the case of Arang, however, the fundamental dilemma is super-well executed (like everything is well executed in this show) and her reaction is a logical consequence of how her character is written. She has no hope. None at all. She is matter of fact and unemotional about her deal with the Gods and hasn't once doubted that she will have to go to either to heaven or hell in a few weeks. A being with no hope simply cannot fathom the kind of love that came their way (and she cannot know what she is turning down). It has been great to see her character grow from an emotionally stunted, very self-centered being in survival-mode to one with a grand heart, that cares deeply for another. It is exactly this slow transformation (and Shin Min-ah's exceptional performance) that makes me have no fear at all for Arang's character in the future. I see many, many, MANY possibilities for buckets of tears ahead, but simply none for messing up one of the finest female KDrama characters ever.