
If she accepts the position of duke, will she still be able to marry Albert, who also has a position of nobility?

I'm not sure. One of the earlier plotlines was that Avery's father had to break his previous engagement because his fiancee refused to give up her title. Apparently if both parties are heirs to an estate, one of them has to give it up for them to get married, or else one family could just collect all the land.

If they merge the estates I think there's no problem, and technically, Avery would be the one with the higher title, so Albert will become Duke by marrying her... But I feel like Avery will leave the title to his cousin (not the one who kidnapped her, the other one, the one she met with the princess)
Let me add some gasoline to this slow burn