How about a craft course? You can get a voucher for a workshop which she can attend at a time of her choosing. So far I have done a Powertex course, glass fusing course, stained glass course, various sewing courses learning different types of sewing, a mosaic course, silver smithing and a silver clay course. There are various lengths of course and some of them have accommodation and food thrown in too. For example, a friend of mine goes on a pottery course somewhere in Devon for an all inclusive weekend of pottery.
Your daughter could do a silver smithing course to make a ring to celebrate this juncture in her life.