In the UK,  when you get engaged, any engagement ring belongs to the person it was given to, even if the marriage doesn’t take place.

(Believe it or not, this is written in law – The Law Reform Act of 1970 says:-

“The gift of an engagement ring shall be presumed to be an absolute gift, this presumption may be rebutted by proving that the ring was given on the condition that it should be returned if the marriage did not take place for any reason.”

But let’s face it, who’s going to put that in writing before proposing?)