This piece of lace has been sewn, together with some fabric flowers, into a piece of pink fabric which has been labelled 'Piece of hangings of the Princess of Wales' boudoir, St George Chapel, March 10: 1863'.
The Princess of Wales was Alexandra of Denmark. On 10 March 1863 she married the eldest son of Queen Victoria, Albert, Prince of Wales, who would become King Edward VII in 1901. It was the first royal wedding to take place at St George’s Chapel in Windsor Castle.
The inscription is similar to those on other objects which belonged to Lady Jane Franklin, so it’s fair to assume this was part of her private museum. We know that she was definitely in England at the time of the wedding, so it's possible she was a guest.