Portrait of a Lady

A central European origin is possible; Germany or perhaps more likely Italy – particularly from the style of the clothing, notably the upper bodice, and heavily puffed and slashed sleeves.  See for instance portraits by Bernadino Luini, Agnolo Bronzino and Bartolomeo Veneto.   The hat with feather, pearls and aglets is a little reminiscent of the cap worn by Joanna of Austria (1535-73), by a follower of Anthonis More (Netherlandish, 1512-1576 – see Royal Collection Trust RCIN 407223.

As to the jewel there are many examples.  The pendant designs by Hans Holbein for instance with jewelled initials (see British Museum)