Elizabeth's position isn't the best possible one. If prince Michel approaches her parents with a good offer, it's easy to see the duke being only too glad to offer her as a wife to Michel. After all, the duke already was ready to throw her to the lions by allowing her to be judged and banished. Like I said in the comments of an earlier chapter, the duke would have most definitely got something out of that deal from the king, otherwise the duke would have lost too much face. This is because at the end of the day nobody could show any concrete evidence against Elizabeth, so she was only judged and sentenced based on what other people claimed. So, if the duke now could sell Elizabeth for a second time, why wouldn't he do it?
Elizabeth's only edge is that she doesn't need to feel any loyalty to her old family/country and more importantly nobody would expect it from her, seeing how she was banished dishonourably. So, Elizabeth wouldn't technically need to care about any orders from her old family, though it would be troublesome if the duke applied pressure on the church. Of course if she just married Leonid, all of her problems would be solved, although naturally she couldn't work as a nun for the church anymore. However, Leonid doesn't seem like a dude who enjoys palaces and the high society, so chances are they would be both perfectly happy living a more rustic life. It's not like Elizabeth wouldn't have a hundred ways of making money using her modern knowledge.