I think whatever you use a room for is what you should call that room! If you sew in it, it will be your sewing room. If you have a bed in it and sleep there it will be a bedroom. So, I hope you are enjoying your larger "sewing room" and I am sure your guests will enjoy being in whatever room they can sit down with you and enjoy your company. It is your home and you should have the freedom to live in it to suite you.