Sister-in-law — used politely for one's spouse's older sister or an older brother's wife.
妻のお義姉さんが遊びに来る予定だ。
My wife's older sister (sister-in-law) is scheduled to visit.
お義姉さんはとても気さくで話しやすい人だ。
My sister-in-law is very friendly and easy to talk to.
結婚してからお義姉さんと仲良くなった。
I became close with my sister-in-law after getting married.
An older stepsister or adopted/otherwise non-blood-related older sister; someone treated like an older sister through family ties.
父が再婚して、お義姉さんができた。
My father remarried, and I got a stepsister.
彼女は血は繋がっていないがお義姉さんのように慕っている。
Although not related by blood, she admires her like an older sister.