I think she's just being realistic. In the first place, you wouldn't assume that somebody likes you just because you know a lot of romantic words or have read a lot of romance genre books. Even if Jade is dropping hints, she's gonna ignore it for the fact that there is a 'fated' female lead for him that is predestined (or as far as she knows).
She doesn't want to deviate too much from the actual storyline because first of all, she isn't sure if those changes will cause her only chance at returning back to her life to be shattered. And right from the start, all she wanted to do is go back home and she needs to make sure that things stay true to the novel to make it back home. She's being logical and using the known method to achieve her goal. She's not viewing this as her new home, she's seeing this world as a barrier to her real home. That's why she's so hell-bent on fixing things up that she thinks she ruined in the past life so that she can get it right and go home as promised.
Next, I'm pretty sure that MC has some sort of inkling that ML likes her but she isn't gonna accept that as fact for a whole lot of reason. Also, let's say she does accept the ML's suit, she would still think about how long it would last and if she does interfere, then the curse wouldn't be broken and ML will suffer. That's on her conscience because she let her 'selfishness' cause the ML's only known chance at being saved to slip away. That would be like asking someone to choose either to let go of their loved one to save them or to keep them by their side and curse them to unbearable suffering.
Of course, if she does choose to be that selfish, then the next would be whether the heart of the ML would change suddenly if the FL of the novel arrives. She's basically setting herself up for heartbreak then. And not everyone is brave enough to go down that thorny path.
ML is pitiful because MC is drawing a clear line and disregarding his affections and his own thoughts. But I think MC is also pitiful because she's someone who gets thrown into a new world with a promise of letting her go back home, maybe, if she does her role in the novel. She's trying so hard to follow the right and known method to get her back home. And in the process, she's hurting the people around her too.
They're both pitiful, and both have their own circumstances. It's basically a matter of perspective at this point. ML wants to not be the emperor to protect MC because he loves her so much. MC wants him to be the emperor to cure his curse plus let her go back home. In the end, both of them have two different things and goals they want to achieve.

The FL. She's annoying.
Very irritating.
How old is she exactly? Living in two lives and then reincarnated should make her wise enough to understand the situation.
But instead, she failed to do so. Not thinking of possibilities or anything. Just like how she wanted to die in that novel world to get back to her real world. Like bruh, you're gonna die in both worlds anyways so why not live the novel's life to the fullest before going to the real world and eventually die there too.
And the fact that she read a novel about romance or she could have read more books in her first life, must mean she knows quite a lot of romantic words or the way a person talks to you..
Does she not think that the ML is in love with her? Or the fact that the current ch right now showed that Jade knows about his past life?
She's quite dense for a whatever years old she is. All and all, I'm here for ML now, not the FL, reading this for my pitiful ML. (づ ̄ ³ ̄)づ