It sounds like you're doing everything you reasonably can to make her feel comfortable and welcome. This is ultimately her issue and there's only so much you, or your husband, or anyone else in the world, can do to address her issue.
So continue to be patient and supportive, keep encouraging her, and give her some time and space to find her comfort zone.
I myself could not go so far as to leave my home to make my husband's love interest comfortable. But clearly that is not an issue for you, so more power to you.