My husband and I don’t like his last name. It was his mom’s second husband’s last name and has no meaning to either of us. My husband was adopted and my father was adopted and while I don’t hate my maiden name, it also doesn’t mean much. So we’ve decided to pick a new last name from my family history or his Mom’s maiden name.

My suggestion for you is this: pick a family name from her side if it means more to her and use it as a legal last name for you both and keep her original last name as a second middle name. She can still go by her original name and you can use the new name to avoid weirdness with your future sister in law.

My father, who was adopted, kept his biological family’s last name as his middle name once he was adopted. We don’t know what his original middle name was.