Princess
Queen, Consort
suffix
The kanji means royal consort, so adding it to someone's name gives you their royal style: "Princess ______," or, in some cases, "Queen ______."
〜妃 essentially refers to the wife of a crown prince, emperor, or other royal family member. These days, you'll almost always see it used with princesses, like ダイアナ妃 (Princess Diana) or キャサリン妃 (Princess Catherine), but in historical contexts you'll occasionally see it used with queen consorts and empress consorts too.
The reading is the same as the one you learned with the kanji.
ダイアナ妃
Princess Diana
キャサリン妃
Princess Catherine
紀子妃
Princess Kiko
フグは、わざとサーモン妃にぶつかりました。
Fugu bumped into Princess Salmon on purpose.
ウィリアム王子とキャサリン妃は、庭を散歩しながら季節の花を楽しみました。
Prince William and Princess Catherine enjoyed seasonal flowers as they walked in the garden.
カナエ妃は子どもたちとの交流をとても大切にしていました。
Princess Kanae really valued interacting with children.
カミラ王妃は、即位前は日本語で「カミラ妃」や「カミラ夫人」と呼ばれました。
Before the accession, Queen Camilla was referred to in Japanese as "Princess Camilla" or "Lady Camilla."