If it only where so easy :')
Spoilers from the novel below.
She can't really, in one life she tries to leave with the knight, but he ends up being killed for eloping with her, also he apparently had a gifriend who shows up and blames her for his death (he is very loyal to fl, not in love with her). In another she tries to leave alone and ends up being sold to a horrible brothel and dies.
I dont remember well since i read the novel months ago, she did went through some tragic events and in the last timeline, she died after protecting her sister. However, at the last minute, crow found her after searching for her in a lot of timelines and after hearing crow calling for her, she suddenly came back to life. So now in the recent chapter, they r on the carriage searching for a place to stay.

The answer is simple. LEAVE
Leave that sorry excuse of a husband and sister. They dont care for you. They're only using you as an excuse to meet eachother by saying they're family since your supposed to marry him. No one in that house respected you since they gave HIM the letter about your family first. That's why you should just leave all these people. Except your knight, you can let him leave with you if you want.