@JWChibi I think she is just anxious because she died going to marry him in the first life, so asking to marry now would be the same as rushing her death.
I think she is just so focus in trying to leave the household she isn't considering other options, like actually being favored by the archduke. She talks about how in the past life he didn't save her, but they didn't have any relationship for him to worry so much + he already said he is having less seizure thanks to her gift, so maybe in the past he was so sick/weak he couldn't do much.
There is also how the marriage would be useful for her family and how in the past life this was all she wanted to do: Be useful to them. Marrying the archduke will not only bound her to her family, but to her "name" as well, and she is trying to preserve her identity now.
So at the same time I think she could accept since the archduke wants more to help/protect her instead of looking to benefit himself and her family, I can understand why she is in denial at first.