Obsessive ex girlfriend

My fiancé moved from Europe to USA years ago. His ex girlfriend cannot wrap her head around the fact that he is engaged, wants nothing to do with her and is starting a family of his own. She’s been obsessively in love with him since she was 16, now 20 despite the crazy distance. Since it didn’t work with him, she’s obsessing over his brothers in their country. If it didn’t work with one, maybe it’ll work with the other/s right???! FFS.